Semiconductor Electronics NEET PYQs (2005–2026) with Solutions

10 solved Semiconductor Electronics PYQs

Real NEET and AIPMT questions from this chapter, newest first. Try each one, then open the answer and the step-by-step explanation.

1. Question 1 (NEET 2026)

   NEET 2026EasyZener diode in reverse breakdown

   An ideal Zener diode with breakdown voltage of $-3\ \mathrm{V}$ is reverse biased with a negative input voltage $V_i = -5\ \mathrm{V}$. The magnitude of voltage difference between point $B$ and $A$ is:

   1. AOption A: $3\ \mathrm{V}$
   2. BOption B: $2\ \mathrm{V}$
   3. COption C: $1\ \mathrm{V}$
   4. DOption D: $0\ \mathrm{V}$

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   Correct answer: (B) $2\ \mathrm{V}$

   Explanation

   The input magnitude (5 V) is larger than the breakdown magnitude (3 V), so the reverse-biased ideal Zener diode is in breakdown and holds exactly 3 V across itself (between $C$ and $B$). The remaining voltage drops across the series resistor $R$, which lies between $B$ and $A$: $|V_{BA}| = 5 - 3 = 2\ \mathrm{V}$. So the answer is option (B).

2. Question 2 (NEET 2026)

   NEET 2026MediumDiodes & Rectifiers

   In the circuit shown below, the voltage appearing across the diode D will be of the form:

   1. AOption A: Circuit 1
   2. BOption B: Circuit 2
   3. COption C: Circuit 3
   4. DOption D: Circuit 4

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   Correct answer: (D) Circuit 4

   Explanation

   The diode becomes reverse biased during the positive half cycle of the input AC signal. When reverse biased: - Current does not flow through the circuit. - Entire input voltage appears across the diode. During the negative half cycle: - Diode becomes forward biased. - Voltage drop across an ideal diode becomes approximately zero. Therefore, voltage across the diode exists only during one half cycle and becomes zero during the other half cycle. Hence the waveform across the diode is a positive half-wave followed by zero. Thus option (D) is correct.

3. Question 3 (NEET 2026)

   NEET 2026EasyPN Junction

   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. Choose the correct answer from the options given below:

   1. AOption A: Both Statements A and B are true
   2. BOption B: Statement A is true, but Statement B is false
   3. COption C: Both Statements A and B are false
   4. DOption D: Statement A is false, but Statement B is true

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   Correct answer: (B) Statement A is true, but Statement B is false

   Explanation

   Above threshold voltage in forward bias, diode current rises sharply, so statement A is true. This current is forward current, not reverse saturation current. Hence statement B is false. Therefore option (B) is correct.

4. Question 4 (NEET 2026)

   NEET 2026MediumDepletion region in forward and reverse bias

   Three identical p-n junction diodes $D_1$, $D_2$, and $D_3$ are connected across a battery as shown in the figure. If the width of the depletion regions of $D_1$, $D_2$ and $D_3$ are $W_1$, $W_2$ and $W_3$, respectively, then the correct option is:

   1. AOption A: $W_1 > W_2 > W_3$
   2. BOption B: $W_3 = W_1 > W_2$
   3. COption C: $W_3 > W_2 > W_1$
   4. DOption D: $W_2 > W_1 = W_3$

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   Correct answer: (C) $W_3 > W_2 > W_1$

   Explanation

   In the figure the battery's positive terminal (longer plate) is on the left, so the left junction is at a higher potential than the right junction. $D_1$ (with a $1\ \mathrm{k\Omega}$ resistor) points to the right: its p-side is at the higher potential, so it is forward biased and its depletion region narrows. $W_1$ is the smallest. $D_2$'s branch is not closed at its right end (there is a gap), so no voltage acts across it. It is unbiased and keeps its equilibrium width $W_2$. $D_3$ points to the left: its n-side is at the higher potential, so it is reverse biased and its depletion region widens. $W_3$ is the largest. Therefore $W_3 > W_2 > W_1$, option (C).

5. Question 5 (NEET 2025)

   NEET 2025EasyLogic Gates & Electronic Devices

   The output (Y) of the given logic implementation is similar to the output of an/a ______ gate.

   1. AOption A: AND
   2. BOption B: NAND
   3. COption C: OR
   4. DOption D: NOR

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   Correct answer: (D) NOR

   Explanation

   The upper gate is NOR with inputs A and B, giving (A + B)'. The lower gate acts as NOT A. These outputs are then ANDed. Simplifying using Boolean algebra gives overall output equivalent to NOR gate.

6. Question 6 (NEET 2025)

   NEET 2025MediumDiodes & Rectifiers

   A full wave rectifier circuit with diodes $(D_1)$ and $(D_2)$ is shown in the figure. If input supply voltage $V_{in}=220\sin(100\pi t)$ volt, then at $t=15\,ms$

   1. AOption A: $D_1$ is forward biased, $D_2$ is reverse biased
   2. BOption B: $D_1$ is reverse biased, $D_2$ is forward biased
   3. COption C: $D_1$ and $D_2$ both are forward biased
   4. DOption D: $D_1$ and $D_2$ both are reverse biased

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   Correct answer: (A) $D_1$ is forward biased, $D_2$ is reverse biased, (B) $D_1$ is reverse biased, $D_2$ is forward biased

   Explanation

   At $t=15\,ms$, $$V_{in}=220\sin(100\pi \times 0.015)$$ $$=220\sin\left(\frac{3\pi}{2}\right)=-220\,V$$ Hence the polarity of the secondary reverses. Depending on the transformer winding convention used in the diagram, either $D_1$conducts and$D_2$ is reverse biased, or vice versa. Therefore both options (A) and (B) are accepted in the official answer key.

7. Question 7 (NEET 2024)

   NEET 2024MediumDiodes & Rectifiers

   Consider the following statements A and B and identify the correct answer: 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.

   1. AOption A: Both A and B are correct.
   2. BOption B: Both A and B are incorrect.
   3. COption C: A is correct but B is incorrect.
   4. DOption D: A is incorrect but B is correct.

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   Correct answer: (C) A is correct but B is incorrect.

   Explanation

   Statement A is incorrect because a solar cell operates in the fourth quadrant (V > 0, I < 0), but the statement as given about I-V characteristics is not fully accurate. Statement B is correct because reverse saturation current in a reverse biased pn junction diode is due to minority carriers, not majority carriers. Therefore, only statement B is correct. Hence, option (D) is correct. NEET 2024 T1 answer key shows Q3 → option (D).

8. Question 8 (NEET 2024)

   NEET 2024EasyLogic Gates & Electronic Devices

   The output $(Y)$ of the given logic gate is similar to the output of an/a:

   1. AOption A: OR gate
   2. BOption B: AND gate
   3. COption C: NAND gate
   4. DOption D: NOR gate

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   Correct answer: (B) AND gate

   Explanation

   The first gate acts as a NOT operation on input $A$, giving $\overline{A}$. The second gate is a NOR gate with single input $B$, equivalent to $\overline{B}$. The final gate is a NOR gate: $$Y = \overline{(\overline{A}+\overline{B})}$$ Using De Morgan's theorem: $$Y = A\cdot B$$ Hence, the overall output is equivalent to an **AND gate**. Therefore, the correct answer is: **(2) AND gate**.

9. Question 9 (NEET 2024)

   NEET 2024MediumLogic Gates & Electronic Devices

   A logic circuit provides the output Y as per the following truth table. The expression for the output Y is:

   1. AOption A: B̅
   2. BOption B: B
   3. COption C: AB + A̅
   4. DOption D: A.B̅ + A̅

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   Correct answer: (A) B̅

   Explanation

   From the truth table: When B = 0, output Y = 1. When B = 1, output Y = 0. Thus output depends only on B and is its complement: $$Y = \overline{B}$$ Hence, option (A) is correct.

10. Question 10 (NEET 2023)

    NEET 2023MediumZener Diode

    Given below are two statements: Statement I : Photovoltaic devices can convert optical radiation into electrical energy. Statement II : Zener diode is designed to operate under reverse bias in breakdown region. In the light of the above statements, choose the most appropriate answer from the options given below :

    1. AOption A: Both Statement I and Statement II are correct.
    2. BOption B: Both Statement I and Statement II are incorrect.
    3. COption C: Statement I is correct but Statement II is incorrect.
    4. DOption D: Statement I is incorrect but Statement II is correct.

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    Correct answer: (A) Both Statement I and Statement II are correct.

    Explanation

    Photovoltaic devices such as solar cells convert light energy into electrical energy. Zener diodes are specially designed to operate in reverse bias under breakdown conditions for voltage regulation. Therefore, both statements are correct.