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Question 1. Which of the following best describes the primary function of a PN junction diode in forward bias? A) Blocks current flow B) Allows current flow with low resistance C) Acts as a constant voltage source D) Converts AC to DC with perfect efficiency Answer: B Explanation: In forward bias, the PN junction diode allows current to flow easily with low resistance, making it useful for rectification. Question 2. What is the main difference between an ideal diode and a practical diode in I-V characteristics? A) Ideal diode has no forward voltage drop, practical diode has a forward voltage drop ( 0 .7V for silicon diodes). Question 3. How does temperature affect the forward voltage of a PN junction diode? A) Increases with temperature B) Decreases with temperature C) Remains constant
D) First increases then decreases Answer: B Explanation: As temperature increases, the forward voltage required to conduct decreases, due to increased carrier activity. Question 4. The static resistance of a diode at a given point is defined as: A) The slope of the I-V curve at that point B) The ratio of voltage to current at that point C) The derivative of current with respect to voltage D) The resistance in the reverse bias region Answer: B Explanation: Static resistance is the ratio of voltage to current at a specific point on the I-V characteristic curve. Question 5. Which capacitance in a PN junction diode is associated with the depletion region? A) Transition capacitance B) Diffusion capacitance C) Junction capacitance D) Transit capacitance
Explanation: Zener breakdown arises from quantum tunneling at high reverse biases, typically at lower voltages compared to avalanche breakdown. Question 8. The primary application of a Zener diode is: A) Rectification B) Voltage regulation C) Signal amplification D) Power switching Answer: B Explanation: Zener diodes are used to maintain a constant voltage across their terminals, functioning as voltage regulators. Question 9. Tunnel diodes operate based on: A) Avalanche effect B) Quantum tunneling C) Thermal emission D) Diffusion of carriers Answer: B Explanation: Tunnel diodes rely on quantum mechanical tunneling through a very narrow depletion layer, enabling fast switching.
Question 10. In a half-wave rectifier, the ripple factor is approximately: A) 0. B) 1. C) 0. D) 0. Answer: A Explanation: The ripple factor for a half-wave rectifier is approximately 0.482, indicating the level of fluctuation in the output. Question 11. The ripple factor of a full-wave bridge rectifier is approximately: A) 0. B) 0. C) 0. D) 0. Answer: D Explanation: The ripple factor for a full-wave rectifier is approximately 0.482, slightly better than half-wave. Question 12. Which filter circuit provides the best smoothing effect for rectified signals?
A) α (alpha) B) β (beta) C) Both α and β D) Neither α nor β Answer: B Explanation: β is the current gain relating base current to collector current in a BJT (β = Ic / Ib). Question 15. Which BJT configuration typically provides high voltage gain but low input impedance? A) Common emitter B) Common base C) Common collector D) Emitter follower Answer: A Explanation: The common emitter configuration offers high voltage gain and moderate input impedance. Question 16. In a BJT hybrid model, the parameter h_FE represents: A) Input impedance
B) Current gain in common emitter configuration C) Voltage gain D) Output resistance Answer: B Explanation: h_FE is the forward current gain (β) in the hybrid model for a BJT. Question 17. The operating point of a BJT is also called: A) Cutoff point B) Q-point C) Saturation point D) Threshold point Answer: B Explanation: The quiescent point (Q-point) is the DC bias point where the BJT operates in its linear region. Question 18. Self-biasing of a BJT involves using: A) A fixed bias resistor B) A voltage divider network C) A biasing transistor
Explanation: At pinch-off, the channel narrows completely, causing the drain current to saturate. Question 21. Enhancement-mode MOSFETs are normally: A) Conducting at zero gate voltage B) Non-conducting at zero gate voltage C) Always on D) Always off Answer: B Explanation: Enhancement-mode MOSFETs are normally off and require a positive gate voltage to conduct. Question 22. In a common source MOSFET amplifier, the output is taken from: A) Drain terminal B) Source terminal C) Gate terminal D) Body terminal Answer: A
Explanation: The common source configuration outputs from the drain terminal, providing voltage amplification. Question 23. Which of the following is NOT a typical characteristic of an ideal operational amplifier? A) Infinite input impedance B) Zero output impedance C) Zero gain D) Infinite open-loop gain Answer: C Explanation: An ideal op-amp has infinite gain, not zero. Question 24. The basic inverting amplifier configuration uses an op-amp with the input signal fed to: A) Non-inverting terminal B) Inverting terminal through a resistor C) Both terminals simultaneously D) Output terminal Answer: B
Explanation: Negative feedback reduces gain but improves bandwidth and stability. Question 27. A class A power amplifier is characterized by: A) Conducting for the entire cycle of input signal B) Conducting only during half of the cycle C) Zero conduction at idle D) High efficiency (>70%) Answer: A Explanation: Class A amplifiers conduct throughout the entire input cycle, offering low distortion but lower efficiency. Question 28. An operational amplifier's input offset voltage is the: A) Voltage required to make the output zero B) Voltage difference between inverting and non-inverting inputs for zero output C) Max voltage it can handle D) The supply voltage Answer: B
Explanation: It is the small voltage difference needed between inputs to produce zero output. Question 29. The basic function of a comparator is to: A) Amplify AC signals B) Compare two voltages and produce a digital output C) Filter noise from signals D) Convert digital signals to analog Answer: B Explanation: Comparators compare two voltages and output a logic level indicating which is higher. Question 30. In a Wien bridge oscillator, the frequency of oscillation depends primarily on: A) The resistor and capacitor values in the RC network B) The inductor and capacitor values C) The crystal frequency D) The supply voltage Answer: A
Question 33. In wave shaping circuits, clipping circuits are used to: A) Remove portions of the waveform exceeding a set level B) Add a DC bias to the waveform C) Convert AC to DC D) Smooth the output waveform Answer: A Explanation: Clipping circuits limit the voltage level of the waveform by "clipping" parts above or below a reference level. Question 34. The primary purpose of a bistable multivibrator is to: A) Generate oscillations B) Store one bit of data C) Amplify signals D) Filter signals Answer: B Explanation: Bistable multivibrators (flip-flops) are used for storing binary data. Question 35. A Schmitt trigger is characterized by: A) Zero hysteresis
B) A hysteresis loop with two different threshold voltages C) Being a linear amplifier D) Only working with AC signals Answer: B Explanation: Schmitt triggers have hysteresis with distinct switching thresholds to prevent false triggering. Question 36. The 555 Timer IC in astable mode produces: A) A single pulse B) A square wave C) A sine wave D) A triangular wave Answer: B Explanation: In astable mode, the 555 timer generates a continuous square wave. Question 37. Which Boolean operation is equivalent to the algebraic law: A + A'B = A + B? A) Absorption law B) Distributive law
Explanation: Full adder sums two bits plus a carry-in, outputting sum and carry-out. Question 40. A multiplexer (MUX) is used to: A) Select one input from multiple inputs B) Convert digital to analog signals C) Store binary data D) Generate clock signals Answer: A Explanation: MUX selects one data input among many based on select lines. Question 41. The characteristic of a synchronous counter is that: A) It counts asynchronously B) All flip-flops are triggered simultaneously by a clock C) It uses only SR flip-flops D) It does not require a clock signal Answer: B Explanation: Synchronous counters have all flip-flops triggered by the same clock, ensuring synchronized counting.
Question 42. In digital logic, the propagation delay is: A) The time it takes for an input change to affect the output B) The maximum frequency of operation C) The voltage difference across a gate D) The delay caused by power supply variations Answer: A Explanation: Propagation delay is the time between input change and output response. Question 43. The CMOS logic family is preferred over TTL mainly because of: A) Faster switching speeds B) Lower power consumption C) Higher propagation delay D) Greater noise immunity at high frequencies Answer: B Explanation: CMOS consumes significantly less power than TTL, especially in static conditions. Question 44. In a ROM, data is stored by: A) Using fusible links or floating gates
