Electronics and Communication questions reward anyone who is comfortable moving between the time domain and the frequency domain. This set covers network theory, analog and digital circuits, signals and systems, control systems, communication systems, and electromagnetics. Numerical solutions keep the units visible at every step, since a dropped factor is the most common reason a correct method still produces a wrong option.
In a common emitter amplifier, the voltage gain is maximum when the load resistance is
Answer: C
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.
Q.2Easy
The input impedance of a common base amplifier is
Answer: B
Common base configuration has very low input impedance (typically 20-100 Ω) because the input is at the emitter which is forward biased.
Q.3Easy
For maximum power transfer in an amplifier circuit, the load impedance should be
Answer: B
Maximum power transfer theorem states that maximum power is delivered when load impedance is the complex conjugate of source impedance (ZL = ZS*).
Q.4Easy
Which configuration provides the highest voltage gain among the three BJT amplifier configurations?
Answer: C
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.
Q.5Easy
An ideal operational amplifier has the following characteristics EXCEPT
Answer: B
Ideal op-amp has: infinite input impedance (Zin→∞), infinite open-loop gain (A→∞), zero output impedance (Zout→0), infinite bandwidth (BW→∞).
Q.6Easy
In a non-inverting amplifier configuration with feedback resistors RF and Ri, the voltage gain is
Answer: A
Non-inverting amplifier gain Av = 1 + (RF/Ri). With RF=0 (short circuit), gain=1 (unity gain buffer). As RF increases, gain increases.
Q.7Easy
An inverting amplifier using op-amp has Rf = 100 kΩ and Rin = 10 kΩ. What is the voltage gain magnitude?
Answer: A
For inverting amplifier, Gain = -Rf/Rin = -100k/10k = -10. The negative sign indicates 180° phase shift.
Q.8Easy
In a Hartley oscillator, the frequency of oscillation is determined by which circuit element combination?
Answer: B
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.
Q.9Easy
Which type of feedback is applied in a non-inverting amplifier configuration?
Answer: B
Non-inverting amplifier uses negative feedback from output to inverting input, which reduces gain but improves linearity, bandwidth, and input impedance.
Q.10Easy
For an ideal op-amp, the input offset voltage is:
Answer: B
An ideal op-amp has zero input offset voltage, zero input bias current, infinite gain, infinite input impedance, and zero output impedance.
Q.11Easy
A transistor amplifier has input signal of 10 mV and output signal of 5 V. What is the voltage gain in dB?
Answer: A
Gain = Vout/Vin = 5V/10mV = 500. Gain (dB) = 20 log₁₀(500) ≈ 54 dB.
Q.12Easy
A power amplifier delivers 100 W to a 8 Ω load. What is the RMS output voltage? (Assuming pure resistive load)
Answer: A
P = V²/R → V = √(P×R) = √(100×8) = √800 ≈ 28.3 V RMS.
Q.13Easy
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.14Easy
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.15Easy
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.16Easy
In a differential amplifier, the Common Mode Rejection Ratio (CMRR) is 80 dB. What is the CMRR in linear form?
