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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 3
6.
A semiconductor diode is biased in forward direction and carrying current I. The current due to holes in p material is
I
0
less than I
0.5
Answer: Option
Explanation:

Small current due to minority carriers also. Therefore hole current is less than.

7.
Between which regions does BJT act like switch?
Cut off and saturation
Cut off and forward active
Forward active and cut off
Saturation and active
Answer: Option
Explanation:

In cut off mode a BJT is an open switch and in saturation mode it is a closed switch.

8.

Assertion (A): When a photoconductive device is exposed to light, its bulk resistance increases.

Reason (R): When exposed to light, electron hole pairs are generated in the photoconductive device.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

A is wrong because exposure to light decreases bulk resistance.

9.
Which of the following elements act as donor impurities?
  1. Gold
  2. Phosphorus
  3. Boron
  4. Antimony
  5. Arsenic
  6. Indium
Select the answer using the following codes :
1, 2 and 3
1, 2, 4, and 6
3, 4, 5 and 6
2, 4 and 5
Answer: Option
Explanation:

Only antimony, arsenic and phosphorous are pentavalent.

10.
Light dependent resistor is
photo resistive device
photo voltaic device
photo emissive device
either (a) or (c)
Answer: Option
Explanation:

Resistance of LDR depends on light.

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