# PN Junction Diode Multiple Choice Questions Answers

## PN Junction Diode Multiple Choice Questions Answers

Que.1 A p-n junction diode’s dynamic conductance is directly proportional to

• (a)The applied voltage
• (b)The temperature
• (c) It’s current
• (d)The thermal voltage

Explanation: PN Junction diode’s dynamic conductance

g_m=\frac{I}{\eta V_t} or g_m \propto I

Que.2 The AC resistance of a forward-biased p-n junction diode operating at a bias voltage ‘V’ and carrying current ‘I’ is

• (a) zero
• (b) a constant value independent of V and I
• (c) V/I
• (d) ΔV/ΔI

Explanation: AC resistance or dynamic resistance r=\frac{\Delta V}{\Delta I}

Que.3 The depletion layer across a p+-n junction lies

• (a) mostly in the p+ – region
• (b) mostly in the n – region
• (c) equally in both the p+and n-regions
• (d) entirely in the p+ – regions

Answer: (b) mostly in the n – region

Explanation: Doping increases so the depletion layer decreases. Therefore, the depletion layer across the p+-n junction lies mostly in the n-region.

Que.4 The change in barrier potential of a silicon p-n junction with temperature is

• (a) 0.0025 Volts per degree C
• (b) 0.0250 Volts per degree C
• (c) 0.0030 Volts per degree C
• (d) 0.0014 Volts per degree C

Answer: (a) 0.0025 Volts per degree C

Que.5 The diffusion capacitance of a p-n junction diode

• (a) Increases exponentially with forwarding bias voltage
• (b) Decreases exponentially with forwarding bias voltage
• (c) Decreases linearly with forwarding bias voltage
• (d) Increases linearly with forwarding bias voltage

Answer: (a) Increases exponentially with forwarding bias voltage

Que.6 The reverse current of a silicon diode is

• (a) Highly bias voltage-sensitive
• (b) Highly temperature sensitive
• (c) Both bias voltage and temperature-sensitive
• (d) Independent of bias voltage and temperature

Explanation: The reverse saturation current of the p-n junction diode depends only on the temperature and is independent of the reverse bias voltage.

Que.7 A combination of two diodes connected in parallel when compared to a single diode can withstand

• (a) Twice the value of peak inverse voltage
• (b) Twice the value of maximum forward current
• (c) A larger leakage current
• (d) Twice the value of cut-in voltage

Answer: (b) Twice the value of the maximum forward current

Que.8 In switching diode fabrication, the dopant is introduced into silicon which introduces additional trap levels in the material thereby reducing the mean lifetime of carriers. This dopant is

• (a) Aluminium
• (b) Platinum
• (c) Gold
• (d) Copper

Explanation: Gold is extensively used as a recombination agent by semiconductor device manufacturers.

Que.9 When a junction diode is used in switching applications, the forward recovery time is

• (a) of the order of the reverse recovery time
• (b) negligible in comparison to the reverse recovery time
• (c) greater than the reverse recovery time
• (d) equal to the mean carrier lifetime for the excess minority carriers.

Answer: (b) negligible in comparison to the reverse recovery time

Que.10 The depletion region in a semiconductor p-n junction diode has

• (a) Electrons and holes
• (b) Positive and negative ions on either side
• (c) Neither electrons nor ions
• (d) No holes

Answer: (b) Positive and negative ions on either side

Que.11 The junction capacitance of a p-n junction depends on

• (a) Doping concentration only
• (b) Applied voltage only
• (c) Both doping concentration and applied voltage
• (d) Barrier potential only

Answer: (c) Both doping concentration and applied voltage

Que.12 When a positive d.c. voltage is applied to the n-side relative to the p-side, a diode is said to be given a

• (a) forward bias
• (b) reverse bias
• (c) zero bias
• (d) neutral bias

Que.13 The depletion layer in a p-n junction is made of which of the following?

• (a) ionized donors on the p-side and ionized acceptors in n-side
• (b) ionized acceptors in p-side donors in n-side and ionized
• (c) Accumulated holes in the p-side and accumulated electrons in n-side
• (d) Accumulated electrons on the p-side and accumulated holes in n-side

Answer: (b) ionized acceptors in p-side donors in n-side and ionized

Que.14 In a step-graded p-n junction diode, what is the ratio of depletion-region penetration depths into p and n regions (if the ratio of acceptor to donor impurity atoms’ densities is 1:2)?

• (a) 2:1
• (b) 4:1
• (c) 1:2
• (d) 1:4

Que.15 What is the typical value for the ratio of current in a p-n junction diode in the forward bias and that in the reverse bias?

• (a) 1
• (c) 100
• (b) 10
• (d) 1000

Que.16 Which junction has the least junction capacitance?

• (a) Alloy
• (b) Grown
• (c) Diffused
• (d) Point Contact

Que.17 A heavily doped semiconductor has

• (a) a resistivity that decreases exponentially with temperature
• (b) a resistivity that rises almost linearly with temperature
• (c) a negative temperature coefficient of resistance
• (d) a positive temperature coefficient of resistance

Answer: (d) a positive temperature coefficient of resistance

Que.18 With the increase of reverse bias in a p-n diode, the reverse current

• (a) decreases
• (b) increases
• (c) remains constant
• (d) may increase or decrease depending upon doping

Que.19 In a semiconductor diode, cut-in voltage is the voltage

• (a) up to which the current is zero
• (b) up to which the current is very small
• (c) at which the current is 10% of the maximum rated current
• (d) at which depletion layer is formed

Answer: (b) up to which the current is very small

Hello friends, my name is Trupal Bhavsar, I am the Writer and Founder of this blog. I am Electronics Engineer(2014 pass out), Currently working as Junior Telecom Officer(B.S.N.L.) also I do Project Development, PCB designing and Teaching of Electronics Subjects.

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