In a Common Source FET amplifier, the gain is primarily dependent on which parameter?
Answer: A
The voltage gain of a CS amplifier is Av = -gm × RD, where gm is transconductance and RD is the drain resistance. This is the fundamental relationship.
Q.242Easy
A BJT amplifier operates in the saturation region. What is the approximate output impedance?
Answer: B
In saturation, the transistor acts almost like a closed switch with minimal voltage drop across it, resulting in very low output impedance.
Q.243Easy
The input impedance of a Common Emitter amplifier is approximately equal to:
Answer: A
The input impedance of a CE amplifier is Zin ≈ β × re, where β is current gain and re is emitter resistance (≈ VT/IE).
Q.244Easy
In a differential amplifier, the Common Mode Rejection Ratio (CMRR) is 80 dB. What is the CMRR in linear form?
A voltage follower (Common Collector) amplifier has a voltage gain of:
Answer: A
The voltage gain of a voltage follower is Av ≈ 1 (or slightly less due to emitter resistance effects). It is used for impedance matching.
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Q.246Medium
An op-amp has an open-loop gain of 100,000 and a feedback resistor ratio of Rf/Rin = 10. What is the closed-loop gain?
Answer: A
For a non-inverting amplifier, Acl ≈ 1 + (Rf/Rin) = 1 + 10 = 11. The feedback dominates over the open-loop gain.
Q.247Medium
In a Colpitts oscillator, the feedback network consists of:
Answer: A
Colpitts oscillator uses capacitive voltage divider with two capacitors in series across an inductor for frequency-determining feedback.
Q.248Medium
A Class B power amplifier has two transistors. What is the primary advantage over Class A?
Answer: A
Class B achieves ~78.5% efficiency by conducting only 180° of the cycle compared to Class A's ~25% efficiency, though it introduces crossover distortion.
Q.249Medium
In a push-pull amplifier configuration, what is the phase relationship between the two transistor inputs?
Answer: A
Push-pull amplifiers use complementary transistors driven 180° out of phase to handle positive and negative half-cycles separately.
Q.250Medium
An inverting amplifier has Rin = 10 kΩ and Rf = 100 kΩ. If the input signal is 100 mV, what is the output voltage?
Answer: A
For inverting amplifier, Vo = -(Rf/Rin) × Vin = -(100k/10k) × 0.1 = -10 × 0.1 = -1 V.
Q.251Easy
In a BJT amplifier biased in the active region, what is the relationship between collector current and base current?
Answer: A
In the active region, IC = β × IB where β is the DC current gain (typically 50-300 for silicon BJTs).
Q.252Medium
Which parameter primarily determines the frequency stability of an RC oscillator?
Answer: A
RC oscillators derive their frequency from RC time constants. The frequency f = 1/(2πRC) approximately, making RC the dominant parameter.
Q.253Easy
An op-amp integrator circuit has R = 10 kΩ and C = 100 nF. What is the time constant?
Answer: A
Time constant τ = RC = 10×10³ × 100×10⁻⁹ = 10×10⁻⁴ = 1×10⁻³ s = 1 ms.
Q.254Hard
In a Common Gate FET amplifier, how does the input impedance compare to Common Source?
Answer: A
CG configuration has low input impedance ≈ 1/gm because the input is presented at the source terminal, acting as a transimpedance amplifier.
Q.255Easy
The gain-bandwidth product (GBW) of a typical general-purpose op-amp (like LM741) is approximately:
Answer: A
LM741 has a GBW product of approximately 1 MHz, which is why it's limited to low-frequency applications. Modern op-amps have higher GBW.
Q.256Hard
In a feedback amplifier with loop gain L = Aβ, the closed-loop gain is approximately:
Answer: A
For negative feedback, Acl = A/(1+L) where L = Aβ is the loop gain. This formula shows how feedback reduces gain but improves stability.
Q.257Medium
A Class AB amplifier operates with a quiescent current (ICQ) that is:
Answer: A
Class AB uses a small quiescent current to bias transistors slightly into conduction, eliminating crossover distortion while maintaining better efficiency than Class A.
Q.258Easy
The input impedance of an op-amp in an ideal configuration is assumed to be:
Answer: A
Ideal op-amp assumptions include infinite input impedance (no current drawn at inputs), zero output impedance, and infinite open-loop gain.
Q.259Easy
In a Common Emitter BJT amplifier, if the collector resistance is increased while keeping other parameters constant, how does the voltage gain change?
Answer: A
Voltage gain Av = -gm × Rc, where gm is transconductance and Rc is collector resistance. Increasing Rc directly increases voltage gain.
Q.260Easy
A non-inverting amplifier is constructed with an op-amp having open-loop gain A₀ = 100,000. If Rf = 90 kΩ and Rin = 10 kΩ, what is the closed-loop voltage gain?
