Electronics (ECE) — MCQ Practice Questions & Answers

Question 1

In a common emitter amplifier, the voltage gain is maximum when the load resistance is

Accepted Answer

Correct answer: C. Much larger than output impedance — Voltage gain AV = gm × RL. Maximum gain occurs when load resistance is much larger than the output impedance of the transistor, limited only by practical considerations.

Answer

A. Very small

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B. Equal to output impedance

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D. Zero

Question 2

The input impedance of a common base amplifier is

Accepted Answer

Correct answer: B. Very low (Ω range) — Common base configuration has very low input impedance (typically 20-100 Ω) because the input is at the emitter which is forward biased.

Answer

A. Very high (MΩ range)

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C. Moderate (kΩ range)

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D. Frequency dependent

Question 3

For maximum power transfer in an amplifier circuit, the load impedance should be

Accepted Answer

Correct answer: B. Complex conjugate of source impedance — Maximum power transfer theorem states that maximum power is delivered when load impedance is the complex conjugate of source impedance (ZL = ZS*).

Answer

A. Equal to source impedance

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C. Much larger than source impedance

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D. Much smaller than source impedance

Question 4

Which configuration provides the highest voltage gain among the three BJT amplifier configurations?

Accepted Answer

Correct answer: C. Common emitter — Common emitter provides both voltage and current gain with gain values typically 100-1000. CB provides only current gain, CC provides only voltage gain close to 1.

Answer

A. Common base

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B. Common collector

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D. All provide same gain

Question 5

An ideal operational amplifier has the following characteristics EXCEPT

Accepted Answer

Correct answer: B. Zero input impedance — Ideal op-amp has: infinite input impedance (Zin→∞), infinite open-loop gain (A→∞), zero output impedance (Zout→0), infinite bandwidth (BW→∞).

Answer

A. Infinite open-loop gain

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C. Infinite bandwidth

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D. Zero output impedance

Question 6

In a non-inverting amplifier configuration with feedback resistors RF and Ri, the voltage gain is

Accepted Answer

Correct answer: A. 1 + RF/Ri — Non-inverting amplifier gain Av = 1 + (RF/Ri). With RF=0 (short circuit), gain=1 (unity gain buffer). As RF increases, gain increases.

Answer

B. 1 - RF/Ri

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C. RF/Ri

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D. Ri/RF

Question 7

An inverting amplifier using op-amp has Rf = 100 kΩ and Rin = 10 kΩ. What is the voltage gain magnitude?

Accepted Answer

Correct answer: A. -10 — For inverting amplifier, Gain = -Rf/Rin = -100k/10k = -10. The negative sign indicates 180° phase shift.

Answer

B. 10

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C. -0.1

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D. 100

Question 8

In a Hartley oscillator, the frequency of oscillation is determined by which circuit element combination?

Accepted Answer

Correct answer: B. Two inductors and one capacitor (LC tank) — Hartley oscillator uses two inductors and one capacitor in the tank circuit. Frequency f = 1/(2π√L_eq×C) where L_eq is equivalent inductance.

Answer

A. Inductor and capacitor only

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C. Resistance and inductance

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D. Two capacitors and resistance

Electronics (ECE) - MCQ Practice Questions