Quick recall · 216 cards
Short MCQ-style retrieval prompts. Tap a card to reveal the answer.
PYQ · 2003
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Generally, the gain of a transistor amplifier falls at high frequency due to the
A · A. Transistor's internal capacitances
PYQ
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In an RC coupled transistor amplifier, which of the following determines the frequency response?
D · D. All of the above
PYQ · 2009
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An ideal op-amp circuit is used as shown in the figure. The output waveform of this circuit will be:
D · Square wave output
PYQ
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A voltage source with voltage \( V_{in} \) is applied to an op-amp circuit. Which of the following correctly describes the behavior of the circuit?
C · It behaves as a current source with current dependent on Vin and resistance
PYQ · 2006
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A relaxation oscillator is constructed using an OPAMP with supply voltages of ±12 V. Determine the voltage waveform characteristics at point P in the circuit.
A · Triangular wave between approximately −12V and +12V with linear rise and fall times
PYQ · 2012
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For Butterworth & Chebyshev filters, which of the following statements is correct?
C · C. Chebyshev response has ripples in the passband
PYQ
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If R = 51 kΩ and C = 0.001 μF, the resonant frequency of a Wien Bridge oscillator is:
A · A) 1.59 kHz
PYQ
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Which of the following is a primary advantage of negative feedback in amplifiers?
C · Increased gain stability
PYQ
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In a negative feedback amplifier, what happens to the bandwidth?
B · Lower cutoff frequency f1 decreases and upper cutoff frequency f2 increases
PYQ
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If the magnitude of the loop gain |T(jω)| > 1 at the frequency where phase(T(jω)) = -180°, what is the stability condition of the feedback amplifier?
B · The amplifier is unstable
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Which statement is correct regarding the gain-bandwidth product in a negative feedback amplifier?
C · It remains constant
PYQ
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The fastest type of Analog to Digital converter is:
(1) Flash ADC
(2) Sigma-Delta ADC
(3) Successive Approximation ADC (SAR)
(4) Dual-Slope ADC
A · Flash ADC
PYQ
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How many equal intervals are present in a 14-bit D-A converter?
A · 16383
For n-bit DAC, number of equal intervals = \( 2^n - 1 \). For 14-bit: \( 2^{14} - 1 = 16384 - 1 = 16383 \). This represents the discrete voltage levels from 0 to full scale.
PYQ
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Which type of ADC is considered the most accurate?
D · Dual Slope ADC
PYQ · 2006
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For a 10-bit digital ramp ADC using 500kHz clock, the maximum conversion time is:
(a) 2048 μs
(b) 2064 μs
(c) 2046 μs
(d) 2084 μs
A · 2048 μs
PYQ
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The number of comparators needed in an 8-bit flash type A to D converter is:
(a) 8
(b) 16
(c) 255
(d) 256
C · 255
Flash ADC requires \( (2^n - 1) \) comparators for n-bit resolution to create 2^n voltage levels. For 8-bit: \( 2^8 - 1 = 256 - 1 = 255 \) comparators.
PYQ
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Arrange the following logic families in the order of increasing speed: CMOS, low power Schottky TTL, ECL, Schottky TTL, low power TTL, TTL
A · CMOS, low power TTL, TTL, low power Schottky TTL, Schottky TTL, ECL
PYQ
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Which logic family has the highest power dissipation per gate?
C · ECL
PYQ · 2020
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If there are m input lines and n output lines for a decoder that is used to uniquely address a byte addressable 1 KB RAM, then the minimum value of m + n is ________.
C · 1034
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How many 2-input multiplexers are required to construct a 2^10 input multiplexer?
A · 1023
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An encoder with 8 inputs will have how many output lines?
B · 3
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How many output lines does a 1-to-8 demultiplexer have?
C · 8
PYQ
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Demultiplexers are used to perform which function?
B · Data distribution
PYQ · 2026
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A 3-bit up counter can be implemented using which type(s) of flip-flop(s)?
A · S-R Flip-flops or D-Flip-flops
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Which of the following best describes the frequency response of a transistor amplifier?
B · Gain decreases at very low and very high frequencies
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Which parameter primarily determines the bandwidth of a transistor amplifier?
C · The frequency range where the gain is within 3 dB of the maximum gain
Bandwidth is defined as the range of frequencies over which the amplifier gain is within 3 dB of its maximum or mid-band gain.
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Refer to the frequency response graph below. What does the point marked as \( f_H \) signify in the frequency response of a transistor amplifier?
C · Higher cutoff frequency where gain falls by 3 dB
The point \( f_H \) marks the higher cutoff frequency, the frequency at which the amplifier gain decreases by 3 dB from its mid-band value due to high-frequency effects.
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In an RC coupled transistor amplifier, which component primarily affects the low-frequency response?
B · Emitter bypass capacitor
The emitter bypass capacitor affects the gain at low frequencies by providing a low reactance path for AC signals, thus improving the low-frequency response.
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How does the coupling capacitor influence the low-frequency cutoff of a transistor amplifier?
B · It decreases the low-frequency cutoff when capacitance increases
Increasing the coupling capacitor value decreases its reactance at low frequencies, thereby lowering the low-frequency cutoff of the amplifier.
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In the bypass capacitor effect on emitter resistance, what happens to the amplifier gain when the capacitor is removed?
B · Gain decreases because emitter resistance limits AC gain
Without the bypass capacitor, the emitter resistance is in AC path, reducing gain at low frequencies due to negative feedback.
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Which of the following transistor internal capacitances has the greatest effect on the high-frequency response?
A · Junction capacitance between collector and base (\( C_{cb} \))
The collector-base junction capacitance \( C_{cb} \) causes the Miller effect, significantly reducing bandwidth at high frequencies.
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How does the Miller effect impact the high-frequency response of a common-emitter transistor amplifier?
A · It increases the input capacitance causing reduced bandwidth
The Miller effect amplifies the collector-base capacitance, increasing the effective input capacitance and reducing the high-frequency bandwidth.
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Refer to the equivalent transistor hybrid-pi model diagram below. Which capacitance corresponds to \( C_{\mu} \) in the model that affects high-frequency roll-off?
B · Collector-base capacitance
\( C_{\mu} \) represents the collector-base junction capacitance, critically affecting the high-frequency response.
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At high frequencies, the dominant factor responsible for the reduction in current gain is:
B · Base transit time and junction capacitances
At high frequencies, the transistor's internal junction capacitances and carrier transit time limit the gain, causing roll-off.
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The gain-bandwidth product (GBW) of a transistor amplifier is defined as:
A · The product of mid-band gain and bandwidth (frequency range between cutoffs)
GBW is a constant product of mid-band gain and bandwidth, representing the trade-off between gain and frequency.
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If a transistor amplifier has a mid-band gain of 50 and an upper cutoff frequency of 100 kHz, what is the gain-bandwidth product?
A · 5 MHz
GBW = Gain \( \times \) Bandwidth = 50 \( \times \) 100,000 Hz = 5,000,000 Hz or 5 MHz.
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Refer to the graph below that shows gain-bandwidth product. If the low-frequency cutoff is 100 Hz and upper cutoff frequency is 1 MHz, what is the bandwidth of the amplifier in Hz?
A · 999,900 Hz
Bandwidth = \( f_H - f_L = 1,000,000 - 100 = 999,900 \) Hz approximately.
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Which equivalent circuit model is commonly used to analyze the frequency response of a bipolar junction transistor (BJT)?
B · Hybrid-pi model
The hybrid-pi model is widely used for frequency response analysis as it includes transistor capacitances and resistances representing BJT behavior.
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Refer to the transistor equivalent circuit diagram below. What does the capacitor \( C_{bc} \) represent in this model?
A · Base-collector junction capacitance
\( C_{bc} \) is the base-collector junction capacitance which influences high-frequency response.
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In the hybrid-pi model, which parameter represents the input resistance affecting the low-frequency response?
A · r_\pi
r_\pi is the input base-emitter resistance that controls the low-frequency equivalent input resistance of the transistor.
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Which transistor amplifier configuration generally offers the widest bandwidth due to its input and output impedances?
B · Common-base (CB)
The common-base configuration typically has wider bandwidth since it has low input capacitance and high-frequency cutoff is higher.
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Compared to a common-emitter (CE) amplifier, the common-collector (CC) amplifier’s high-frequency response is generally:
A · Wider bandwidth due to low output impedance
The CC amplifier (emitter follower) typically exhibits wider bandwidth due to its low output impedance and absence of Miller effect.
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Calculate the bandwidth of a transistor amplifier if the lower -3dB frequency is 20 Hz and the upper -3dB frequency is 20 kHz.
A · 19,980 Hz
Bandwidth = \( f_H - f_L = 20,000 - 20 = 19,980 \) Hz.
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For an amplifier, the mid-band gain is 40, the lower cutoff frequency is 50 Hz and the upper cutoff frequency is 500 kHz. What is the gain-bandwidth product?
A · 20 MHz
GBW = Gain \( \times \) Bandwidth = 40 \( \times \) (500,000-50) \( \approx 20 \times 10^6 \) Hz = 20 MHz.
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Refer to the diagram representing an RC coupled amplifier circuit below. Which component primarily determines the lower cutoff frequency?
A · Coupling capacitor (C_c)
The coupling capacitor and the resistance it interacts with form a high-pass filter determining the low-frequency cutoff.
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What is the primary factor determining the mid-band gain of a transistor amplifier?
B · Transistor's current gain (\( \beta \)) and load resistance
Mid-band gain primarily depends on the transistor's current gain and load resistance. Other factors mainly affect frequency response at low or high frequencies.
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Which frequency range corresponds to the mid-band region in a transistor amplifier’s frequency response?
A · Between low-frequency cutoff and high-frequency cutoff
The mid-band region lies between the low-frequency and high-frequency cutoff points where gain is approximately constant.
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In the frequency response of a transistor amplifier, the gain starts to fall beyond which frequency-related parameter?
B · High-frequency cutoff
Beyond the high-frequency cutoff, the amplifier's gain typically decreases due to parasitic capacitances and transistor limitations.
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Which of the following internal capacitances in a bipolar junction transistor has the most significant effect on the high-frequency response?
B · Collector-base junction capacitance
Collector-base junction capacitance reduces the high-frequency gain by creating a feedback path that becomes significant at high frequencies.
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The decrease in gain at low frequencies in a transistor amplifier is mainly due to:
A · Coupling and bypass capacitor reactance increasing
At low frequencies, coupling and bypass capacitors behave like high reactance, causing gain to fall due to signal attenuation.
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For a transistor amplifier, if the low-frequency cutoff is 20 Hz and the high-frequency cutoff is 1 MHz, the approximate bandwidth is:
B · 980 kHz
Bandwidth is calculated as \( f_H - f_L = 1\,MHz - 20\,Hz = 980\,kHz \).
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Refer to the frequency response plot below. What is the cause of the steep gain drop at the high-frequency region?
B · Effect of transistor's internal capacitances and Miller effect
The rapid gain fall at high frequencies is due to internal transistor capacitances, particularly the Miller capacitance, limiting bandwidth.
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The mid-band gain of an amplifier is 40 dB and the bandwidth is 20 kHz. Which of the following statements is correct if the gain-bandwidth product (GBW) is constant?
B · If the gain increases to 60 dB, bandwidth will halve
Gain-bandwidth product (GBW) is constant; increasing gain reduces bandwidth proportionally.
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If a transistor amplifier has a mid-band gain of 100 (40 dB) and a bandwidth of 10 kHz, what is the gain-bandwidth product (GBW)?
C · 100 kHz
GBW = Gain × Bandwidth = 100 × 10 kHz = 1,000,000 Hz = 100 kHz.
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What is the significance of the 3-dB frequency in the frequency response of transistor amplifiers?
A · Frequency where output power is half of its mid-band value
3-dB frequency defines the cutoff point where output power drops to half, corresponding to a \( \sqrt{2} \) drop in voltage gain magnitude.
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Which type of transistor amplifier typically has the widest frequency response with relatively flat gain over a broad bandwidth?
B · Direct coupled amplifier
Direct coupled amplifiers have a very wide frequency response starting from DC because they do not use coupling capacitors, resulting in flat gain over a broad bandwidth.
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Refer to the simplified RC coupled amplifier circuit below. Which components primarily determine the low-frequency cutoff?
A · Input coupling capacitor and emitter bypass capacitor
The low-frequency cutoff is mainly set by the reactance of input coupling and emitter bypass capacitors, which block low-frequency signals at high reactance.
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Among the following transistor amplifier types, which one typically exhibits frequency response limitations mainly due to the transformer's frequency range rather than the transistor itself?
B · Transformer coupled amplifier
Transformer coupled amplifiers’ frequency response is limited by the transformer’s core and winding inductance, restricting bandwidth.
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Gain-bandwidth product (GBW) of a transistor amplifier is 2 MHz. For a desired gain of 50, what maximum bandwidth can be expected?
A · 40 kHz
Bandwidth \( = \frac{GBW}{Gain} = \frac{2\,MHz}{50} = 40\,kHz \). However, careful reading shows option A is 40 kHz, so this matches the calculation.
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If the gain-bandwidth product of a transistor amplifier is constant, which of the following statements is TRUE when the gain is reduced by half?
B · Bandwidth doubles
Since GBW is constant, if gain halves, bandwidth doubles to maintain the product.
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The gain-bandwidth product of a transistor amplifier is 5 MHz. When the gain is increased from 20 to 50, what happens to the bandwidth?
A · Bandwidth reduces from 250 kHz to 100 kHz
Bandwidth = GBW / Gain. For gain 20: bandwidth = 5 MHz / 20 = 250 kHz; for gain 50: bandwidth = 5 MHz / 50 = 100 kHz.
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Which of the following is NOT an ideal characteristic of an operational amplifier?
C · Infinite input bias current
An ideal op-amp has zero input bias current, but infinite input bias current is not an ideal characteristic.
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In practical operational amplifiers, the input offset voltage is usually due to:
A · Mismatch in input transistors
Input offset voltage arises mainly due to mismatches in the input transistors of the op-amp.
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Refer to the diagram below of an inverting amplifier. If the input resistor \( R_1 = 10\,k\Omega \) and the feedback resistor \( R_f = 100\,k\Omega \), what is the voltage gain \( A_v \)?
A · -10
For an inverting amplifier, \( A_v = - \frac{R_f}{R_1} = -\frac{100k}{10k} = -10 \).
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A non-inverting amplifier has \( R_1 = 5\,k\Omega \) and \( R_f = 45\,k\Omega \). What is the voltage gain of the amplifier?
A · 10
Non-inverting gain is \( A_v = 1 + \frac{R_f}{R_1} = 1 + \frac{45k}{5k} = 1 + 9 = 10 \).
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Which of the following expressions correctly represents the output voltage of a difference amplifier with resistors \( R_1 = R_3 \) and \( R_2 = R_4 \)?
A · \( V_{out} = \frac{R_2}{R_1} (V_2 - V_1) \)
For a difference amplifier with perfectly matched resistors \( R_1 = R_3 \) and \( R_2 = R_4 \), the output is \( V_{out} = \frac{R_2}{R_1} (V_2 - V_1) \).
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Refer to the diagram below of a difference amplifier with \( R_1 = R_3 = 10\,k\Omega \) and \( R_2 = R_4 = 20\,k\Omega \). If \( V_1 = 3V \) and \( V_2 = 7V \), what is the output voltage \( V_{out} \)?
A · 8V
Output voltage is \( V_{out} = \frac{R_2}{R_1} (V_2 - V_1) = \frac{20k}{10k}(7 - 3) = 2 \times 4 = 8V \).
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What is the output voltage expression of an ideal integrator op-amp circuit with input voltage \( V_{in} \), input resistor \( R \) and feedback capacitor \( C \)?
A · \( V_{out} = -\frac{1}{RC} \int V_{in} \; dt \)
The integrator output voltage is \( V_{out} = -\frac{1}{RC} \int V_{in} dt \).
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Which of the following is a primary application of comparator circuits using operational amplifiers?
A · To compare two input voltages and provide digital output
Comparators compare two voltages and output a high or low voltage corresponding to which input is higher, effectively converting analog to digital output.
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Refer to the diagram below of a comparator circuit with reference voltage \( V_{ref} = 2V \). If the input voltage \( V_{in} \) varies from 0V to 5V, what will be the output voltage \( V_{out} \) when \( V_{in} = 3V \)?
A · +15V (positive saturation)
Since \( V_{in} > V_{ref} \), the comparator output saturates at positive supply voltage, typically +15V.
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Which of the following characteristics is NOT typical of an ideal operational amplifier?
D · Non-zero output impedance
An ideal op-amp has zero output impedance to drive any load without voltage drop. Non-zero output impedance is a non-ideal characteristic.
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If an ideal op-amp is connected in an inverting amplifier configuration with \(R_f = 100\,k\Omega\) and \(R_{in} = 10\,k\Omega\), and input voltage \(V_{in} = 1\,V\), what is the output voltage \(V_{out}\)?
A · -10 V
Inverting amplifier gain is \( -\frac{R_f}{R_{in}} = -\frac{100k}{10k} = -10 \). Therefore, \(V_{out} = -10 \times 1 = -10 V\).
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Refer to the circuit diagram below of a non-inverting amplifier. If \(R_1 = 5\,k\Omega\) and \(R_2 = 15\,k\Omega\), what is the voltage gain \(A_v\) of the amplifier?
A · 4
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Refer to the circuit diagram of a difference amplifier below. If \(R_1 = R_3 = 10\,k\Omega\) and \(R_2 = R_4 = 100\,k\Omega\), what is the output voltage \(V_{out}\) given \(V_1 = 2 V\) and \(V_2 = 5 V\)?
A · 30 V
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Which function best describes the output voltage \(V_{out}\) of an op-amp integrator circuit with input voltage \(V_{in}\), resistor \(R\), and capacitor \(C\)?
A · \(V_{out} = -\frac{1}{RC} \int V_{in}\, dt\)
The output voltage of an ideal op-amp integrator is \(V_{out} = -\frac{1}{RC} \int V_{in} dt\), indicating inversion and integration scaled by \(1/RC\).
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Refer to the waveform diagram below of an op-amp differentiator's output when a triangular input wave is applied. What is the shape of the output waveform?
A · Square wave
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Which of the following best describes the zero-crossing detector circuit's output response when the input signal crosses zero volts?
A · Output swings to the positive saturation voltage
A zero-crossing detector outputs the positive saturation voltage when its input crosses from negative to positive, effectively detecting the zero crossing by switching output states.
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In a voltage follower (buffer) circuit, what is the ideal voltage gain and input/output impedance behavior?
A · Gain = 1; High input impedance; Low output impedance
Voltage followers have unity gain, very high input impedance, and low output impedance, ideal for impedance matching.
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Which of the following is TRUE regarding an instrumentation amplifier made from op-amps?
C · It offers high CMRR and high input impedance
Instrumentation amplifiers are designed to offer high common-mode rejection ratio (CMRR) and high input impedance, suitable for precise low-level signals.
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Which practical limitation of an op-amp causes distortion in the output signal when the input changes very rapidly?
B · Slew rate limitation
Slew rate limits how fast the output of an op-amp can change; if input changes faster than this rate, distortion occurs due to output lag.
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Refer to the frequency response graph below of a typical op-amp. What effect does the gain-bandwidth product impose on the amplifier's frequency and gain relationship?
A · Gain decreases as frequency increases to keep the product constant
Gain-bandwidth product is constant for an op-amp; thus, as frequency increases, gain must decrease proportionally to maintain this product.
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Which of the following is NOT a characteristic of an active filter compared to passive filters?
C · Can only realize low-pass and high-pass configurations
Active filters can realize low-pass, high-pass, band-pass, and band-stop configurations, unlike passive filters which have limitations.
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The primary advantage of using active filters over passive filters is:
C · Improved frequency selectivity with gain
Active filters provide gain and better frequency selectivity due to incorporation of active components like op-amps.
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In an active filter, which component primarily determines the cutoff frequency?
B · Resistor and capacitor values
Cutoff frequency in active filters is mainly determined by the resistors and capacitors forming the frequency-dependent network.
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Which of the following describes the magnitude response of a Butterworth filter?
A · Maximally flat in the passband and monotonic in both passband and stopband
Butterworth filters have a maximally flat response in the passband and a smooth monotonic roll-off in the stopband.
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For an nth order Butterworth low-pass filter, the magnitude squared response is given by \( |H(j\omega)|^2 = \frac{1}{1 + (\frac{\omega}{\omega_c})^{2n}} \). What does \( \omega_c \) represent?
A · Cutoff angular frequency
\( \omega_c \) is the cutoff frequency where the magnitude response is \( \frac{1}{\sqrt{2}} \) of the maximum, defining the filter bandwidth.
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Refer to the diagram below showing the frequency response of a 3rd order Butterworth low-pass filter with cutoff frequency \( f_c = 1 \text{ kHz} \). What is the expected gain at the cutoff frequency?
B · \( \frac{1}{\sqrt{2}} \) (≈ -3 dB)
At cutoff frequency, the Butterworth filter gain drops to \( \frac{1}{\sqrt{2}} \) or approximately -3 dB from the passband gain.
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Which of the following is a key feature in the design of a Chebyshev Type I filter?
B · Ripple in passband and monotonic stopband
Chebyshev Type I filters exhibit passband ripple and a monotonic stopband.
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The advantage of employing a Chebyshev filter instead of Butterworth is:
B · Sharper cutoff with the same filter order
Chebyshev filters provide a steeper roll-off than Butterworth for the same order by accepting passband ripple.
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Which polynomial is used in Chebyshev filter magnitude squared response?
C · Chebyshev polynomial
Chebyshev filters use Chebyshev polynomials to define the equiripple passband response.
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Refer to the diagram below of magnitude responses of Butterworth and Chebyshev Type I filters of the same order. Which statement is TRUE?
A · Chebyshev has steeper roll-off but visible passband ripple
Chebyshev filters trade ripple in passband for steeper roll-off compared to Butterworth filters.
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The roll-off rate of an active Butterworth filter of order \( n \) is:
A · \( 20n \text{ dB/decade} \)
The Butterworth filter's roll-off rate is 20 dB/decade per order, so total roll-off is \( 20n \text{ dB/decade} \).
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Which statement correctly describes the frequency response of a Chebyshev Type I low-pass filter?
C · Ripple in passband and monotonic in stopband
Chebyshev Type I filters exhibit passband ripple and a monotonic stopband response.
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Refer to the frequency response graph below of a high-order Butterworth and Chebyshev filter pair. Which filter shows ripple and why?
C · Chebyshev due to passband ripple characteristic
Chebyshev Type I filters have ripple in the passband owing to their equiripple design approach.
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If an active low-pass Butterworth filter of order 4 has a cutoff frequency \( f_c = 1 \text{ kHz} \), what is the roll-off rate beyond the cutoff?
D · 80 dB/decade
Roll-off rate = 20 dB/decade × order = 20 × 4 = 80 dB/decade.
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Determining the order of an active Butterworth low-pass filter requires knowledge of:
B · Cutoff frequency and desired attenuation at a given stopband frequency
Filter order is chosen based on cutoff frequency and required attenuation at stopband to meet design specs.
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The poles of an nth order Butterworth low-pass filter lie on:
A · The left half of the complex plane evenly spaced on a circle
Butterworth filter poles lie on the left half plane equally spaced in angle on a circle of radius equal to the cutoff frequency.
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Refer to the pole-zero plot diagram below of a 3rd order Butterworth filter. How are the pole positions distributed?
B · Three poles evenly spaced at 120° intervals in left half-plane
The 3rd order Butterworth filter poles are placed equally spaced by 120° around a semicircle in the left half-plane.
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In Chebyshev filter design, the filter order increases to achieve:
B · Sharper transition band
Increasing the filter order in Chebyshev filters improves roll-off sharpness, making transition band narrower.
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Which of the following is true about zeros in Butterworth and Chebyshev low-pass filters?
C · Both have zeros only at infinity
Butterworth and Chebyshev low-pass filters are all-pole filters with zeros only at infinity.
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Refer to the pole-zero diagram below. For a 4th order Chebyshev filter with 0.5 dB passband ripple, which is the correct pole placement pattern?
A · Poles lie symmetrically in left half-plane on ellipse
Chebyshev poles are placed on an ellipse in the left half-plane depending on passband ripple value.
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Which of the following is a practical implementation advantage of active filters?
B · Op-amps allow easy gain adjustment
Active filters use op-amps which allow straightforward gain and frequency response adjustment without inductors.
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Which active filter configuration commonly uses an operational amplifier with resistors and capacitors to realize a low-pass filter?
A · Sallen-Key
The Sallen-Key configuration is widely used for implementing active low-pass filters.
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Refer to the circuit schematic below of an active low-pass Sallen-Key filter. The cutoff frequency is primarily set by:
B · The capacitor and resistor values
The cutoff frequency is determined by the resistor and capacitor values in the Sallen-Key network.
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Which of the following factors critically affects the stability of an active filter circuit?
C · Pole locations in the left half of s-plane
Stability requires poles to be inside the left half of the s-plane; this governs filter stability.
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An active filter system shows multiple poles very close to the imaginary axis. What impact does this have on filter performance?
C · Potential instability and ringing in time response
Poles near imaginary axis cause slow decay and oscillatory ringing, risking instability.
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Which of the following best describes a practical disadvantage when implementing a high-order active filter?
A · Greater power consumption and increased noise
High-order active filters consume more power, produce more noise, and are more complex.
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Which active filter implementation technique is most suitable for integrated circuit fabrication due to its simple topology?
C · Sallen-Key filters
Sallen-Key filters are simple, use fewer components, and are frequently used in IC fabrication.
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When comparing Butterworth and Chebyshev filters for the same order, which statement is TRUE regarding group delay?
C · Butterworth has more linear group delay, causing less phase distortion
Butterworth filters have smoother and more linear phase response resulting in less signal distortion compared to ripple-influenced Chebyshev filters.
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A key practical difference between Butterworth and Chebyshev active filters is:
B · Chebyshev filters have steeper roll-off but introduce passband ripple
Chebyshev filters achieve faster roll-off by allowing passband ripple; Butterworth filters are ripple-free but have gentler rolloff.
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Refer to the comparison table below showing key differences between Butterworth and Chebyshev filters. Which characteristic differentiates them most clearly regarding passband behavior?
B · Chebyshev has equiripple passband, Butterworth is maximally flat
Butterworth filters have maximally flat passbands; Chebyshev filters exhibit equiripple passband response.
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The main trade-off when designing a filter using Chebyshev instead of Butterworth is:
B · Passband ripple versus sharper cutoff
Chebyshev filters trade passband ripple for sharper cutoff characteristics compared to Butterworth.
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Refer to the combined frequency response diagram below comparing Butterworth and Chebyshev filters. Which filter demonstrates a more rapid cut-off rate for the same filter order?
B · Chebyshev filter
Chebyshev filters have a faster roll-off rate than Butterworth filters for the same order due to allowed ripple.
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Which filter type would be preferred if a maximally flat group delay is critical in a communication system?
B · Butterworth
Butterworth filters have smooth phase response and relatively linear group delay compared to Chebyshev, thereby preserving signal integrity better.
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What is the primary advantage of an active filter over a passive filter?
B · They have gain and can provide signal amplification
Active filters use amplifying devices like op-amps, enabling them to provide gain, unlike passive filters which cannot amplify signals.
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Which of the following components is essential in an active filter design?
C · Operational Amplifier
Active filters typically use operational amplifiers along with resistors and capacitors to achieve desired frequency responses without inductors.
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In an active low-pass filter, what is the role of the feedback resistor?
B · To establish the gain of the filter
The feedback resistor in an active filter circuit sets the gain by controlling how much output signal is fed back to the input.
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Given an active filter with cut-off frequency \( f_c = 1\text{kHz} \) and gain of 10, which parameter primarily controls the bandwidth?
C · Resistor and capacitor values determining the cut-off
The resistor and capacitor values in the filter control the cut-off frequency and thus effectively define the bandwidth of the filter.
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Why are active filters preferred over passive filters in audio applications?
A · Because active filters have lower distortion
Active filters provide amplification and better control over filter characteristics, resulting in lower distortion and improved performance for audio signals.
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The undesirable frequency components in an active filter are attenuated primarily by which characteristic?
B · Roll-off rate of the filter
The roll-off rate (slope of attenuation) determines how sharply unwanted frequencies are attenuated beyond the cut-off frequency.
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Which condition defines a Butterworth filter's magnitude response?
A · Maximally flat amplitude response in the passband
The Butterworth filter is designed to have a maximally flat frequency response in the passband without ripples.
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The -3 dB cut-off frequency of a Butterworth filter is defined as the frequency where the power drops to what fraction of its maximum?
A · One half
At the -3 dB point, the output power drops to half of its maximum value.
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Refer to the diagram below showing the frequency response curve of a Butterworth filter.
What is the slope of attenuation per octave beyond the cut-off frequency for a second-order Butterworth filter?
A · 12 dB/octave
Each order contributes 6 dB/octave roll-off. For a second-order Butterworth filter, the roll-off is 12 dB/octave.
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Which polynomial defines the denominator of the Butterworth filter's transfer function?
C · Maximally flat polynomial
Butterworth filters use a maximally flat polynomial as the denominator to ensure a flat passband response.
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In a third-order Butterworth low-pass filter, the pole locations are:
A · Equally spaced on a circle in the left-half s-plane
Poles of a Butterworth filter lie equally spaced on a circle in the left half of the s-plane to ensure stability and flatness of response.
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One major characteristic of a Chebyshev filter is the presence of ripples in which frequency band?
A · Passband only
Chebyshev filters exhibit equiripple behavior in the passband, resulting in ripples there, but have a monotonic stopband.
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The Chebyshev filter achieves a steeper roll-off than Butterworth filter by allowing what?
B · Ripple in the passband
Allowing ripple in the passband allows the Chebyshev filter to achieve a steeper roll-off compared to the maximally flat Butterworth filter.
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Refer to the pole-zero plot below of a Chebyshev filter.
Why do the poles lie closer to the imaginary axis compared to Butterworth filter poles?
A · Because of the ripple allowance in passband
Chebyshev filter poles are placed closer to the imaginary axis to allow ripple in the passband and achieve a faster roll-off compared to Butterworth.
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Which of the following best describes the passband ripple magnitude in a Chebyshev Type I filter?
B · Equal ripple amplitude throughout the passband
Chebyshev Type I filters have equiripple (equal amplitude ripples) in the passband throughout its range.
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What is the effect of increasing the ripple factor in a Chebyshev filter on its transition band?
A · Narrows the transition band
Larger ripple in the passband allows for a sharper (narrower) transition band with faster roll-off.
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A 4th-order Butterworth filter has a -3 dB bandwidth of 1 kHz. What can be said about its roll-off beyond cutoff frequency?
A · 24 dB/octave
Each order contributes 6 dB/octave, so a 4th order filter's roll-off is 4 × 6 = 24 dB/octave.
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Which design parameter primarily influences the steepness of the filter’s transition band?
A · Filter order
The order of the filter determines how quickly the filter attenuates frequencies outside the passband, thus affecting transition steepness.
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If a Chebyshev filter of order 3 shows 0.5 dB passband ripple, increasing the filter order to 5 while keeping ripple constant will:
A · Increase the steepness of roll-off
Higher order results in a sharper roll-off, improving suppression of unwanted frequency components.
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Which design parameter is NOT part of the Butterworth filter specifications?
A · Passband ripple
Butterworth filters have no passband ripple and thus it is not a design parameter.
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The transfer function of an nth-order Butterworth low-pass filter at cut-off frequency \( \omega_c \) satisfies which of the following?
A · \( |H(j\omega_c)| = \frac{1}{\sqrt{2}} |H(0)| \)
At the cutoff frequency, the Butterworth filter has a magnitude of \( 1/\sqrt{2} \) times the maximum gain (which corresponds to -3 dB).
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Refer to the Bode plot below of an active filter. What is the approximate bandwidth of this filter if the -3 dB points are at 500 Hz and 5 kHz?
A · 4.5 kHz
Bandwidth is the difference between the upper and lower -3 dB frequencies: 5000 Hz - 500 Hz = 4500 Hz or 4.5 kHz.
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Which characteristic of the frequency response curve distinguishes an active Chebyshev filter from an active Butterworth filter?
A · Presence of passband ripple
Chebyshev filters show passband ripples due to design, whereas Butterworth filters have a maximally flat passband without ripples.
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The phase response of a Butterworth filter is best described as:
A · Non-linear with phase distortion
Butterworth filters have a non-linear phase response leading to some phase distortion especially near the cut-off frequency.
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Which of the following frequency response graphs corresponds to a Chebyshev filter with 1 dB ripple? Refer to the diagram below.
A · Graph A with ripples in the passband
The Chebyshev filter is identified by equiripple behavior in the passband (Graph A).
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Which of the following is a commonly used op-amp configuration for implementing active low-pass filters?
A · Inverting amplifier with RC feedback
An inverting amplifier with RC components in the feedback path is a standard configuration for active low-pass filters.
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Refer to the circuit diagram below of an active filter. Which component mainly determines the cut-off frequency?
A · Capacitor value
In an active RC filter, the capacitor value along with resistor value sets the cutoff frequency.
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In practical active filter circuits, what is the main reason op-amps are preferred over other devices?
A · High input impedance and low output impedance
Op-amps provide high input impedance and low output impedance making them ideal for active filter designs.
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Which active filter implementation technique provides the best linearity and lowest noise for audio applications?
A · Using op-amps with buffered integrators
Active filters implemented with op-amps employing buffered integrator circuits provide excellent linearity and low noise for audio frequencies.
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Which table option correctly compares Butterworth and Chebyshev active filters given below? Refer to the diagram below.
A · Butterworth: maximally flat, slower roll-off; Chebyshev: ripple in passband, faster roll-off
Butterworth filters have maximally flat response but slower roll-off, while Chebyshev filters have passband ripple and faster roll-off.
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Which active filter type provides better selectivity with the same order and cutoff frequency?
A · Chebyshev
Chebyshev filters offer better selectivity due to their steeper roll-off from passband ripple allowance.
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What is a practical disadvantage of Chebyshev active filters compared to Butterworth?
A · Passband distortion due to ripple
The passband ripple in Chebyshev filters can lead to signal distortion, which may be undesirable in some applications.
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Which application is most suited for Butterworth filters rather than Chebyshev filters?
A · Audio signal processing requiring flat amplitude
Butterworth filters provide flat amplitude response suitable for audio processing where distortion must be minimized.
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What practical consideration must be made for active filter design when implementing in high-frequency applications?
A · Op-amp gain-bandwidth limit
Op-amps have gain-bandwidth limitations that constrain filter performance at high frequencies.
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Which of the following is NOT usually a concern in the practical implementation of active filters?
D · Quantum tunneling on resistors
Quantum tunneling is not a practical design concern for electronic passive and active components at this scale.
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Which of the following is a necessary condition for sustained oscillations in an oscillator circuit according to Barkhausen criteria?
A · The loop gain must be equal to one and the phase shift must be zero or an integral multiple of 2\pi radians
Barkhausen criteria require the product of gains in the feedback loop to be unity (loop gain = 1) and the total phase shift around the loop to be zero or multiple of 2\pi for sustained oscillations.
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Which parameter primarily determines the frequency of oscillation in an RC oscillator?
C · Both resistors and capacitors
In RC oscillators, the frequency of oscillation depends on both the resistance and capacitance values in the frequency selective network.
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Which of the following statements about oscillator frequency stability is TRUE?
C · Frequency stability is better in LC oscillators compared to RC oscillators
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Refer to the diagram below of a basic feedback oscillator circuit.
If the forward gain of the amplifier is 10 and the feedback fraction is 0.1, what is the loop gain and will oscillations start?
A · Loop gain = 1; Oscillations will start
Loop gain is product of amplifier gain and feedback fraction: 10 x 0.1 = 1. According to Barkhausen criteria, oscillations start when loop gain equals 1.
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Refer to the Colpitts oscillator circuit below. If \( L = 10\,\mu H \), \( C_1 = 100\,pF \), and \( C_2 = 100\,pF \), calculate the frequency of oscillation (in MHz).
A · 15.9 MHz
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In a Colpitts oscillator, what is the primary role of capacitors \( C_1 \) and \( C_2 \)?
A · They form a voltage divider to provide feedback
Capacitors \( C_1 \) and \( C_2 \) form a capacitive voltage divider which samples the oscillation voltage and provides the required feedback for sustaining oscillations.
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Which one is an advantage of the Colpitts oscillator over the Hartley oscillator?
D · Less sensitive to stray capacitances
Colpitts oscillator uses capacitors for feedback reducing the effect of stray inductances, making it less sensitive to stray capacitances compared to the inductive-tapped Hartley oscillator.
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Refer to the Colpitts oscillator circuit diagram below. If the transistor's gain changes, which component(s) ensure the oscillations remain stable?
A · The capacitive voltage divider formed by \( C_1 \) and \( C_2 \)
The capacitive voltage divider controls the amount of feedback voltage, thereby maintaining stable oscillations despite variations in transistor gain.
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What is the distinguishing feature of a Hartley oscillator's feedback network compared to the Colpitts oscillator?
A · It uses an inductive voltage divider instead of a capacitive one
Hartley oscillator uses two inductors or a tapped inductor as an inductive voltage divider for feedback, unlike the capacitive voltage divider in Colpitts.
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Refer to the Hartley oscillator circuit below. If the inductors \( L_1 = 5\,\mu H \) and \( L_2 = 10\,\mu H \) are connected in series with capacitor \( C = 100\,pF \), calculate the frequency of oscillation.
B · 15.9 MHz
Total inductance \( L = L_1 + L_2 = 15 \mu H \).Frequency \( f = \frac{1}{2\pi \sqrt{L C}} = \frac{1}{2\pi \sqrt{15 \times 10^{-6} \times 100 \times 10^{-12}}} \approx 15.9\,MHz \).
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In the Hartley oscillator, if the ratio \( \frac{L_1}{L_2} \) is increased, the amplitude of output oscillation generally...
A · Increases due to higher feedback fraction
Increasing the ratio \( \frac{L_1}{L_2} \) increases feedback voltage fraction, which increases output oscillation amplitude up to saturation point.
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Which one of these is an inherent drawback of Hartley oscillator circuits compared to Colpitts?
A · More prone to stray inductance effects causing frequency drift
Hartley oscillators depend on inductors for feedback which are more susceptible to stray inductances and magnetic coupling causing frequency drift.
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Refer to the Hartley oscillator circuit diagram below. What is the function of the tapped inductor in the circuit?
A · To provide the necessary feedback for sustained oscillations
The tapped inductor acts as an inductive voltage divider providing the feedback necessary to satisfy the Barkhausen criteria for oscillations.
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Which of the following components form the frequency determining network in a Wien Bridge oscillator?
A · Two resistors and two capacitors in a lead-lag configuration
Wien Bridge oscillator uses a lead-lag RC network consisting of two resistors and two capacitors arranged to provide frequency selective feedback.
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Refer to the Wien Bridge oscillator circuit below. If \( R_1 = R_2 = 10\,k\Omega \) and \( C_1 = C_2 = 0.01\,\mu F \), what is the oscillator frequency?
A · 1591 Hz
Frequency \( f = \frac{1}{2\pi R C} = \frac{1}{2\pi \times 10,000 \times 0.01 \times 10^{-6}} \approx 1591 Hz \).
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One primary benefit of the Wien Bridge oscillator is:
A · It produces very low distortion sine waves
Wien Bridge oscillators are well known for producing low distortion sinusoidal outputs, making them ideal for audio frequencies.
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What is the standard value of the closed-loop gain required in a Wien bridge oscillator to satisfy the Barkhausen criteria for oscillation?
A · 3
The non-inverting amplifier gain in a Wien bridge oscillator must be set to 3 to make the loop gain exactly one to satisfy Barkhausen criteria.
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Refer to the Wien bridge oscillator with amplitude stabilisation circuit shown below. Which component is primarily responsible for amplitude stabilization?
A · Light bulb or thermistor in the feedback loop
A light bulb or thermistor is placed in the feedback path to provide automatic amplitude control by changing resistance with temperature, stabilizing output amplitude.
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Which of the following conditions is necessary for sustained oscillations in any oscillator circuit?
A · Loop gain is greater than 1 and the phase shift is 0° or multiples of 360°
For sustained oscillations, the loop gain must be unity or greater and the total phase shift around the loop must be 0° or multiples of 360°, as per the Barkhausen criteria.
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An oscillator circuit converts which type of input signal into a continuous waveform output?
A · No input signal (zero input) to sustained output oscillations
Oscillators generate continuous waveforms without any external input signal by using their internal circuit feedback, converting zero input into sustained oscillations.
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Refer to the diagram below of a generic feedback oscillator.
Which part of the circuit is principally responsible for determining the oscillation frequency?
A · Frequency selective network in the feedback path
The frequency selective network in the feedback path sets the frequency at which the loop gain and phase conditions satisfy oscillation criteria.
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Which one of the following statements about oscillators is TRUE?
C · Oscillators convert DC power into AC signals with a specific frequency
Oscillators convert DC power into AC signals of a certain frequency by using frequency-selective feedback circuits.
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In a Colpitts oscillator, which component combination determines the frequency of oscillation?
A · An inductor and two capacitors connected as a voltage divider
The Colpitts oscillator uses an LC tank circuit where frequency is set by an inductor and two capacitors forming a capacitive voltage divider in the feedback path.
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Why is the capacitive voltage divider used in Colpitts oscillator’s feedback network?
C · To produce the required feedback voltage for oscillation
The capacitive voltage divider provides an appropriate fraction of the output signal as feedback to sustain oscillations.
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Calculate the frequency of oscillation of a Colpitts oscillator where \(L = 10\,\mu H\), \(C_1 = 100\,pF\), and \(C_2 = 100\,pF\). Use \(f = \frac{1}{2 \pi \sqrt{L C}}\), where \(C = \frac{C_1 C_2}{C_1 + C_2}\).
C · \(79.6\,MHz\)
First calculate \(C = \frac{100 \times 100}{100 + 100} = 50\,pF = 50\times10^{-12} F\). Then, \(f=\frac{1}{2\pi \sqrt{10\times10^{-6} \times 50\times10^{-12}}} = 79.6MHz\).
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Refer to the diagram below of a Colpitts oscillator circuit.
Which of the following will increase the oscillation frequency?
B · Decreasing the values of capacitors C1 and C2
The frequency is inversely proportional to the square root of LC. Decreasing capacitance will increase frequency.
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Refer to the diagram below of a Hartley oscillator.
If the inductors \(L_1\) and \(L_2\) are equal, what will be the effective inductance \(L\) in the frequency formula \(f=\frac{1}{2 \pi \sqrt{L C}}\)?
A · Sum of \(L_1\) and \(L_2\), i.e., \(L = L_1 + L_2\)
Inductors in series add up, so effective inductance is \(L = L_1 + L_2\), assuming negligible mutual inductance.
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In a Hartley oscillator circuit, feedback ratio is mainly controlled by:
A · The ratio of the inductances in the tapping (\(L_1 / L_2\))
The feedback voltage in Hartley oscillator depends on the inductive voltage divider formed by \(L_1\) and \(L_2\).
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Given a Hartley oscillator with \(L_1 = 20\,\mu H\), \(L_2 = 30\,\mu H\), and capacitor \(C = 200\,pF\), calculate the oscillation frequency (in MHz). Use \(f = \frac{1}{2 \pi \sqrt{L C}}\) where \(L = L_1 + L_2\).
D · 22.5 MHz
Total inductance \(L = 20 + 30 = 50 \mu H = 50 \times 10^{-6} H\), capacitance \(C = 200 \times 10^{-12} F\). \(f = \frac{1}{2\pi\sqrt{50 \times 10^{-6}\times 200 \times 10^{-12}}} = 22.5 MHz\).
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Refer to the Hartley oscillator diagram below.
If the feedback tap moves nearer to the grounded end (reducing \(L_1\)), what is the expected effect on oscillations?
A · Feedback decreases, oscillation may stop
Reducing \(L_1\) reduces the feedback voltage ratio, possibly falling below the required level to sustain oscillations.
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The Wien bridge oscillator is commonly preferred in audio frequency generation because:
B · It produces low distortion sine wave output using RC network
Wien bridge oscillator uses an RC frequency selective network that produces low distortion sine waves suitable for audio frequencies.
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Refer to the circuit diagram below of a Wien bridge oscillator.
Which components set the oscillation frequency \(f_0\) of the oscillator?
A · Resistors \(R_1, R_2\) and capacitors \(C_1, C_2\)
The oscillation frequency is determined by the RC network: \(f_0 = \frac{1}{2\pi R C}\), typically with \(R_1 = R_2 = R\) and \(C_1 = C_2 = C\).
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What is the main advantage of using an automatic gain control (AGC) circuit in a Wien bridge oscillator?
A · To stabilize amplitude and reduce distortion of output waveform
AGC maintains constant amplitude by automatically adjusting gain, reducing distortion in Wien bridge oscillator output.
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Determine the frequency of oscillation for a Wien bridge oscillator having \(R = 10\,k\Omega\) and \(C = 5\,nF\). Use \(f = \frac{1}{2 \pi R C}\).
D · 15.9 kHz
\(f = \frac{1}{2 \pi \times 10 \times 10^3 \times 5 \times 10^{-9}} = 15.9 kHz\).
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Refer to the frequency response graph of a Wien bridge oscillator below.
At frequency \(f_0\), what should be the magnitude of the loop gain for sustained oscillations?
A · Exactly 1 (unity gain)
For sustained oscillations, the loop gain magnitude at \(f_0\) should be unity according to the Barkhausen criteria.
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What is a primary purpose of using feedback in an amplifier circuit?
B · To stabilize the gain and improve linearity
Feedback is mainly used to stabilize the gain, improve linearity, reduce distortion, and control bandwidth in amplifiers.
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In a feedback amplifier, which of the following is TRUE about the feedback signal?
C · It is a portion of the output fed back to the input
The feedback signal is a portion of the output signal that is fed back to the input to influence the amplifier’s performance.
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In which of the following scenarios does negative feedback NOT improve amplifier performance?
C · Increasing gain
Negative feedback typically reduces the gain but improves linearity, bandwidth, and stability.
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Identify the type of feedback where the feedback signal adds to the input signal, potentially causing oscillations.
D · Both B and C
Positive feedback (also called regenerative feedback) adds to the input signal and can lead to oscillations.
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Which type of feedback is commonly used in amplifiers to improve gain stability and reduce distortion?
B · Negative feedback
Negative feedback reduces gain variations and distortion, improving stability and linearity.
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Refer to the diagram below showing voltage feedback amplifier configuration. What type of feedback is used if the feedback voltage is derived from output voltage and fed in series at input voltage?
C · Series-series feedback
Feedback voltage fed in series with input voltage is called series feedback, and when derived from output voltage, it is series-series feedback.
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Which of the following is the necessary condition for a feedback amplifier to be stable?
B · Loop gain magnitude \( |A\beta| < 1 \) at 0° or 360° phase shift
For stability, the magnitude of loop gain must be less than unity when the phase shift is 0° or 360° to prevent sustained oscillations.
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The Barkhausen criterion states that oscillations will occur when the product of gain and feedback satisfies which condition?
B · \( |A\beta| = 1 \) and total phase shift is 0° or 360°
Barkhausen criterion requires loop gain magnitude equal to unity and total phase shift around the loop to be 0° or an integer multiple of 360° for oscillations to start.
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Which of the following statements about phase margin is correct?
A · Phase margin is the difference between 180° and the phase shift at unity gain frequency
Phase margin is the amount of additional phase shift required to bring the system to the point of oscillation (i.e., 180° phase shift) at unity gain frequency.
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Refer to the Bode plot diagram below. What is the approximate phase margin of the amplifier if the gain crosses 0 dB at 1 kHz and the phase at this frequency is \(-130°\)?
A · 50°
Phase margin = 180° - |Phase at 0 dB crossover| = 180° - 130° = 50°.
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What does a gain margin of 10 dB indicate for a feedback amplifier?
A · The gain can increase by 10 dB before instability occurs
Gain margin of 10 dB means the amplifier's gain can increase by 10 dB before hitting the critical point of instability (gain magnitude |Aβ|=1 at 180° phase shift).
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If an amplifier has a gain margin of 5 dB and a phase margin of 60°, what can be said about its stability?
B · It has adequate stability margins
A phase margin of around 60° and a gain margin above 0 dB typically indicate good stability in the amplifier.
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Which of the following is a common technique used to improve the stability of a feedback amplifier?
B · Adding a lead compensator network
Adding a lead compensator introduces phase advance, improving phase margin and thus enhancing stability.
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Refer to the diagram below showing an amplifier with a compensation network. What is the primary purpose of the RC network shown across the amplifier?
B · To provide lead compensation for stability improvement
The RC network provides lead compensation by advancing phase, which helps to increase phase margin and stabilizes the amplifier.
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Which effect does negative feedback have on the input impedance of a voltage amplifier?
B · Increases input impedance
Negative feedback in a voltage amplifier usually increases the input impedance by feeding back a portion of the output in a manner that opposes changes at the input.
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Negative feedback in an amplifier generally causes which of the following changes to the output impedance?
B · Output impedance decreases
Negative feedback tends to reduce output impedance, making the amplifier better at driving loads.
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Refer to the Nyquist plot diagram below of a feedback amplifier. At which point would the amplifier become unstable based on the plot?
A · When the plot encircles the point (-1, 0) on the complex plane
According to Nyquist criterion, instability occurs if the Nyquist plot encircles the critical point (-1 + j0).
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Which of the following correctly describes the significance of the phase crossover frequency in frequency response analysis for stability?
B · Frequency where phase shift is -180°
Phase crossover frequency is the frequency at which the total phase shift around the feedback loop is -180°, critical for assessing stability.
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A unity-gain frequency of a feedback amplifier is 1 MHz, and its phase margin is 20°. What is the likely stability condition of this amplifier?
B · Marginally stable and prone to ringing
A low phase margin (~20°) indicates marginal stability leading to overshoot and ringing in the transient response.
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Refer to the Bode plot diagram below showing gain and phase characteristics of an amplifier. At the frequency where the gain crosses 0 dB, the phase plot shows -210°. What is the phase margin and stability implication?
A · Phase margin = -30°, amplifier is unstable
Phase margin = 180° - |Phase at gain crossover| = 180° - 210° = -30°, indicating phase margin is negative and the amplifier is unstable.
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What is the primary function of a multiplexer (MUX) in digital circuits?
A · To select one input from many inputs and forward it to a single output
A multiplexer selects one of many inputs based on select lines and forwards that selected input to a single output.
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Refer to the diagram below showing a 4-to-1 multiplexer. If select lines S1S0 are 10, which input will be connected to the output?
C · I3
For select inputs S1S0 = 10 (binary 2), the multiplexer connects input I3 to the output since inputs are numbered from I0 to I3.
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Which of the following is a common application of a multiplexer?
B · Data selection and routing
Multiplexers are widely used for selecting and routing data from many inputs to a single output line.
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A 16-to-1 multiplexer has how many select lines?
C · 4
Number of select lines required is \( \log_2(16) = 4 \).
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What is the output of a 3-to-8 decoder when the inputs are 101 and enable is asserted?
A · The output line corresponding to decimal 5 is HIGH
The input 101 in binary corresponds to decimal 5. When enable is asserted, only output Y5 is HIGH.
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Refer to the truth table below of a 2-to-4 decoder with enable. Which output is active when inputs \( A=1 \), \( B=0 \), and Enable \( E=1 \)?
A · Y2
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Which statement about decoders is TRUE?
A · A decoder converts binary inputs into a set of outputs with only one output active at a time
A decoder takes an n-bit binary input and activates only one of its 2^n outputs corresponding to the input code.
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In combinational circuit design, which one is TRUE regarding the use of multiplexers and decoders?
A · Multiplexers can be used to implement any Boolean function by selecting variable combinations
Multiplexers can be configured to implement any Boolean function by using inputs as variables and selecting lines to choose minterms.
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Designing a combinational circuit to realize the function \( F = \sum m(1,3,5,7) \) using a 4-to-1 multiplexer, which inputs should be connected to the data inputs?
A · Apply inputs \( x,y \) on select lines and connect inputs as 0,1,0,1 for I0 to I3
Applying variables on select lines and mapping minterm outputs to data inputs allows the multiplexer to implement the function correctly: inputs correspond to function values at input combinations.
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Which of the following shows a valid method to implement \( F = A \cdot B + \overline{A} \cdot C \) using a 4-to-1 multiplexer?
D · Use \( A, B \) on select lines and data inputs as C, 0, 1, 0
By using variables \( A \) and \( B \) on select lines, data inputs are connected to the function values for each input combination; hence, mapping C, 0, 1, 0 realizes the function.
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In a decoder circuit, what is the role of an enable input?
A · To activate the decoder outputs only when enable is HIGH
Enable input controls whether the decoder operates; outputs are active only if enable is asserted (HIGH). Otherwise, all outputs remain inactive (usually LOW).
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Refer to the block diagram below of a 2-to-4 decoder with enable input. If enable \( E=0 \) and input select lines are \( 11 \), what is the status of the outputs?
A · All outputs are LOW
When enable input is LOW, the decoder outputs are disabled; hence all outputs remain LOW regardless of input values.
