NEET Semiconductor Electronics PYQs & Practice Questions

10 free NEET Physics questions on Semiconductor Electronics, starting with previous year questions (2016–2026). Tap “Show answer” to check each one. No login needed.

Topics: Logic Gates · Full Wave Rectifier · Logic Gate Combination - NOT + NOR = AND · Solar Cell I-V Characteristics and Reverse Biased Diode Current · Logic Gate Truth Table - Boolean Expression · Photovoltaic Device and Zener Diode · Logic Gates - NOT-NOR Combination · p-n Junction Diode - Depletion Region Width · Zener Diode as Voltage Regulator · p-n Junction Diode Circuits · Logic Gate Truth Table · CE Transistor Amplifier

Q1NEET 2026p-n Junction Diode - Depletion Region Width
Three identical p-n junction diodes D1, D2 and D3 are connected across a 5V battery with their respective 1kOhm resistors in a circuit as shown (D1 and its resistor in one branch, D2 and its resistor in a second parallel branch, D3 and its resistor in a third parallel branch, with D3 oriented in reverse relative to D1 and D2). If the width of the depletion regions of D1, D2 and D3 are W1, W2 and W3, respectively, then the correct option is:
- A. W3 = W1 > W2
- B. W3 > W2 > W1
- C. W2 > W1 = W3
- D. W1 > W2 > W3
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Answer: A — W3 = W1 > W2
D1 and D2 are forward biased in the circuit (current flows through them, reducing their depletion region width), while D3 is reverse biased (increasing its depletion region width). Due to the differing branch configurations and resistances, the forward bias across D2 is less than that of D1, leading to depletion width ordering W3 > W2 > W1, with D3 (reverse biased) having the widest depletion region.
Q2NEET 2026Zener Diode as Voltage Regulator
An ideal Zener diode with breakdown voltage of −3 V is reverse biased with a negative input voltage Vᵢ = −5 V, connected in series with a resistor R (points C-diode-B-R-A, with the battery completing the circuit from A back to C). The magnitude of voltage difference between points B and A is:
- A. 2 V
- B. 1 V
- C. 0 V
- D. 3 V
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Answer: —
Since the Zener diode is reverse biased and the applied voltage magnitude (5 V) exceeds the breakdown voltage (3 V), the diode breaks down and clamps the voltage across itself (between C and B) at 3 V in magnitude. The remaining voltage drops across the resistor R (between B and A): |Vᵢ| - |V_breakdown| = 5 - 3 = 2 V. So the magnitude of the voltage difference between B and A is 2 V.
Q3NEET 2026p-n junction diode bias statements
Two statements are given below: A. When the forward bias voltage across a p-n junction diode increases above a certain threshold voltage, the diode current increases significantly. B. This current is called reverse saturation current.
- A. Both Statements A and B are true
- B. Both Statements A and B are false
- C. Statement A is true, but Statement B is false
- D. Statement A is false, but Statement B is true
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Answer: B — Both Statements A and B are false
A is true; the current described is forward current, not reverse saturation current, so B is false.
Q4NEET 2026Diode voltage waveform
In the circuit shown below, the voltage appearing across the diode D will be of the form:
- A. Waveform per option (1)
- B. Waveform per option (2)
- C. Waveform per option (3)
- D. Waveform per option (4)
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Answer: C — Waveform per option (3)
Per the given circuit and the official key, the voltage across diode D matches the pattern shown in option 4.

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Q5NEET 2025Logic Gates
The output (Y) of the given logic implementation (A, B into a NOR gate, A, B into a NAND gate, both outputs into an AND gate) is similar to the output of an/a ____ gate.
- A. AND
- B. NAND
- C. OR
- D. NOR
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Answer: C — OR
Y1 = (A+B)' (NOR), Y2 = (A.B)' (NAND), Y = Y1·Y2 = (A+B)'·(A'+B') = (A'B').(A'+B') = A'B' = (A+B)', which is the NOR gate output.
Q6NEET 2025Full Wave Rectifier
A full wave rectifier circuit with diodes (D1) and (D2) is shown in the figure (centre-tapped transformer feeding D1 and D2 into load RL). If input supply voltage Vin = 220 sin(100πt) volt, then at t = 15 msec
- A. D1 is forward biased, D2 is reverse biased
- B. D1 is reverse biased, D2 is forward biased
- C. D1 and D2 both are forward biased
- D. D1 and D2 both are reverse biased
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Answer: A — D1 is forward biased, D2 is reverse biased
f = 100π/2π = 50 Hz, so period T = 1/50 = 20 ms. At t = 15 ms, the signal is in its negative half cycle (negative from 10ms to 20ms), so the secondary voltage polarity makes D1 reverse biased and D2 forward biased.
Q7NEET 2024Logic Gate Combination - NOT + NOR = AND
The output (Y) of the given logic gate is similar to the output of an/a: [Figure: Input A through a NOT gate, Input B through a NOR gate (with itself), both outputs into a NOR gate giving output Y]
- A. OR gate
- B. AND gate
- C. NAND gate
- D. NOR gate
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Answer: A — OR gate
Y = NOT(NOT(A) + NOT(B)) = NOT(NOT(A)) · NOT(NOT(B)) = A·B (by De Morgan's theorem), which is the AND gate output.
Q8NEET 2024Solar Cell I-V Characteristics and Reverse Biased Diode Current
Consider the following statements A and B and identify the correct answer: [Graph: I-V axes divided into quadrants I, II, III, IV] A. For a solar-cell, the I-V characteristics lies in the IV quadrant of the given graph. B. In a reverse biased pn junction diode, the current measured in (μA), is due to majority charge carriers.
- A. Both A and B are correct.
- B. Both A and B are incorrect.
- C. A is correct but B is incorrect.
- D. A is incorrect but B is correct.
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Answer: B — Both A and B are incorrect.
Statement A is correct - for a solar cell, the I-V characteristic curve lies in the fourth quadrant since it acts as a power source (negative current, positive voltage convention). Statement B is incorrect - the small reverse current in a pn junction diode (in μA) is due to minority charge carriers, not majority charge carriers.

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Q9NEET 2024Logic Gate Truth Table - Boolean Expression
A logic circuit provides the output Y as per the following truth table: A B Y 0 0 1 0 1 0 1 0 1 1 1 0 The expression for the output Y is:
- A. B̄ (NOT B)
- B. B
- C. A.B + Ā
- D. A.B̄ + Ā
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Answer: —
From the truth table, Y=1 only when B=0 (regardless of A's value: A=0,B=0→Y=1; A=1,B=0→Y=1), and Y=0 when B=1. So Y = B̄ (NOT B), independent of A.
Q10NEET 2023Full Wave Rectifier
A full wave rectifier circuit consists of two p-n junction diodes, a center-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output?
- A. p-n junction diodes
- B. Capacitor
- C. Load resistance
- D. A center-tapped transformer
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Answer: A — p-n junction diodes
The capacitor acts as a filter in the rectifier circuit, charging during peaks and discharging during troughs, which smooths out the pulsating DC output and removes the AC ripple.

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