1. Given below are two statements:

Statement I : Photovoltaic devices can convert optical radiation into electricity.

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 : ⇒ (NEET 2023)

A. Both Statement I and Statement II are incorrect.

B. Statement I is correct but Statement II is incorrect.

C. Statement I is incorrect but Statement II is correct.

D. Both Statement I and Statement II are correct

The Correct Answer is (D)

Statement I : Photocell/solar cell convert light energy into electric energy/current.

Statement II : We use zener diode in reverse biased condition, when reverse biased voltage more than break down voltage than it act as stablizer.

2. The incorrect statement about the property of a Zener diode is : ⇒ ( NEET 2022 Phase 2)

A. and n regions of Zener diode are heavily doped

B. Zener voltage remains constant at breakdown

C. It is designed to operate under reverse bias

D. Depletion region formed is very wide

The Correct Answer is (A)

Zener diode is special purpose p-n junction diode, which is generally operated in reverse bias for its operation of voltage regulation. It is a heavily doped p-n junction. Due to large doping concentration depletion width is narrower.

3. Consider the following statements (A) and (B) and identify the correct answer.

(A) A Zener diode is connected in reverse bias, when used as a voltage regulator.

(B) The potential barrier of p-n junction lies between 0.1 V to 0.3 V. ⇒ (NEET 2021)

A. (A) is incorrect but (B) is correct.

B. (A) and (B) both are correct.

C. (A) and (B) both are incorrect.

D. (A) is correct and (B) is incorrect.

The Correct Answer is (D)

In reverse biased, after breakdown, voltage across the zener diode becomes constant. Therefore zener diode is connected in reverse biased when used as voltage regulator.

for Ge Potential barrier V₀ = 0.3 V

Si Potential barrier V₀ = 0.7 V

4. The given graph represents V-I characteristic for a semiconductor device. ⇒ (AIPMT 2014)

AIPMT 2014 Physics - Semiconductor Electronics Question 92 English

Which of the following statement is correct ?

A. It is V-I characteristic for solar cell where, point A represents open circuit voltage and point B short circuit current.

B. It is for a solar cell and popints A and B represent open circuit voltage and current, respectively.

C. It is for a photodiode and points A and B represent open circuit voltage and current, respectively.

D. It is for a LED and points A and B represent open circuit voltage and short circuit current, respectively.

The Correct Answer is (A)

The V-I characteristic for a solar cell is as shown the figure.

AIPMT 2014 Physics - Semiconductor Electronics Question 92 English Explanation

5. A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in figure. The current through the diode is ⇒ (AIPMT 2011 Mains)

AIPMT 2011 Mains Physics - Semiconductor Electronics Question 72 English

A. 5 mA

B. 10 mA

C. 15 mA

D. 20 mA

The Correct Answer is (A)

Voltage across 250 Ω resistance = 20 V – 15 V = 5 V

Now current through 250 $Ω$ resistance: 5/250 = 20 mA

If voltage across load resistance 1 k $Ω$ is 15 V, then

current through 1 kΩ is 15/1000 = 15 mA

The current through the zener diode is

= Current through 250 $Ω$ resistance – Current through 1 k $Ω$ resistance.

= 20 - 15

= 5 mA

6. A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength ⇒ (AIPMT 2009)

A. 4000 nm

B. 6000 nm

C. 4000 $\overset{\circ}{A}$

D. 6000 $\overset{\circ}{A}$

The Correct Answer is (C)

$λ$ _max = $\frac{h c}{E}$

= $\frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{2.5 \times 1.6 \times 10^{- 19}}$

= 5000 $\overset{o}{A}$

Now the wavelength detected by photodiode be less than $λ$ _max, hence it can detect a signal of wave length 4000 $\overset{o}{A}$ .

7. A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly ⇒ (AIPMT 2008)

A. 1 $\times$ 10¹⁴ Hz

B. 20 $\times$ 10¹⁴ Hz

C. 10 $\times$ 10¹⁴ Hz

D. 5 $\times$ 10¹⁴ Hz

The Correct Answer is (D)

Energy gap E_g = 2.0 eV

E_g = 2.0 × 1.6 × 10^–19 J

E_g = hf

f = frequency of radiation

$∴$ f = $\frac{E_{g}}{h}$

= $\frac{3.2 \times 10^{- 19}}{6.625 \times 10^{- 34}}$

5 $\times$ 10¹⁴ Hz

8. Zener diode is used for ⇒ (AIPMT 2005)

A. amplification

B. rectification

C. stabilisation

D. producing oscillations in an oscillator.

The Correct Answer is Option (B)

Zener diode is used for stabilisation while p-n junction diode is used for rectification.

9. In a p-n junction photo cell, the value of the photo-electromotive force profuced by monochromatic light is proportional to ⇒ (AIPMT 2005)

A. The barrier voltage at the p-n junction.

B. The intensity of the light falling on the cell.

C. The frequency of the light falling on the cell.

D. The voltage applied at the p-n junction.

The Correct Answer is Option (B)

Electromotive force depends on intensity of light that falls on it and does not depend on the frequency.

⇒ Semiconductor

Topic 5 : Special Purpose Diode