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.
Which semiconductor memory loses its data when power is switched off?
Answer: C
DRAM (Dynamic RAM) is volatile and requires periodic refreshing. Data is lost without power, unlike non-volatile memories like ROM, EEPROM, and Flash.
Q.62Easy
What is the truth table output for a D flip-flop when CLK = 1 and D = 1?
Answer: B
In a D flip-flop, Q takes the value of D on the clock edge. When D = 1, Q becomes 1 and Q' becomes 0.
Q.63Easy
What is the output of a full adder when A=1, B=1, and Cin=1?
Answer: C
Full adder: A+B+Cin = 1+1+1 = 3 (binary 11). Sum = 1, Carry out = 1.
Q.64Easy
In a 8×4 RAM configuration, what do 8 and 4 respectively represent?
Answer: B
In RAM notation m×n, m represents number of addressable locations and n represents bits per location.
Q.65Easy
In a JK flip-flop, what happens when both J and K inputs are 1?
Answer: B
When J=1 and K=1, the JK flip-flop enters toggle mode, changing its state with each clock pulse.
Q.66Easy
A multiplexer with 16 inputs requires how many select lines?
Answer: C
For 2^n inputs, n select lines are needed. For 16 = 2^4 inputs, 4 select lines are required.
Q.67Easy
In a 3-bit binary counter, how many clock pulses are needed to complete one full cycle?
Answer: C
A 3-bit counter can count from 000 to 111 (0 to 7 in decimal), requiring 2^3 = 8 clock pulses to complete one full cycle.
Q.68Easy
Which of the following is a non-volatile memory type commonly used in embedded systems?
Answer: C
Flash memory is non-volatile (retains data without power), widely used in embedded systems, SSDs, and microcontrollers as program storage.
Q.69Easy
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.70Easy
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.71Easy
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.72Easy
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.73Easy
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.74Easy
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.75Easy
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.76Easy
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.77Easy
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.78Easy
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.79Easy
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.80Easy
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.
