# Electronics and Communication Engineering - Electronic Devices and Circuits

16.

Assertion (A): When light falls at junction of p-n photodiode, its p side becomes positive and n side becomes negative.

Reason (R): When a photodiode is short circuited, the current in the external circuit flows from p side to n side.

 A. Both A and R are true and R is correct explanation of A B. Both A and R are true but R is not a correct explanation of A C. A is true but R is false D. A is false but R is true

Explanation:

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17.

In what condition does BJT act like an open switch

 A. cut off B. saturation C. active D. both (b) and (c)

Explanation:

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18.

In a JFET

 A. gate source cut off voltage is equal to VDS B. gate source cut off voltage is equal to pinch off voltage C. gate source cut off voltage is twice the pinch off voltage D. gate source cut off voltage is equal to negative pinch off voltage

Explanation:

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19.

A power supply has full-load voltage of 20 V. What will be its no load voltage when its voltage regulation is 100%

 A. 0 V B. 10 V C. 20 V D. 40 V

Explanation:

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20.

For a photo conductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in the intensities of optical illumination results in

 A. change in open circuit voltage B. change in short circuit current C. a reduction resistance D. an increase of resistance