1

### AIPMT 2014

The barrier potential of a p-n junction depends on
(1)   type of semiconductor material
(2)   amount of doping

(3)   temperature

Which one of the following is correct ?
A
(1) and (2) only
B
(2) only
C
(2) and (3) only
D
(1), (2) and (3)

## Explanation

The barrier potential depends on type of semiconductor (For Si, Vb = 0.7 V and for Ge, Vb = 0.3 V), amount of doping and also on the temperature.
2

### AIPMT 2014

The given graph represents V-I characteristic for a semiconductor device.

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.

## Explanation

The V-I characteristic for a solar cell is as shown the figure.
3

### NEET 2013 (Karnataka)

One way in which the operation of a n-p-n transistor differs from that of a p-n-p
A
The emitter junction injects minority carries into the base region of the p-n-p
B
The emitter injects holes into the base of the p-n-p and electrons into the base region of n-p-n
C
The emitter injects holes into the base of n-p-n
D
The emitter junction is reversed biased in n-p-n

## Explanation

In p-n-p transistor holes are injected into the base while electrons are injected into the base of n-p-n transistor. Emitter-base junction is forward biased.
4

### NEET 2013

The output (X) of the logic circuit shown ion figure will be

A
X = A . B
B
X = $\overline {A + B}$
C
X = $\overline {\overline A } .\overline {\overline B }$
D
X = $\overline {A.B}$

## Explanation

The output of the given logic circuit is

X = $\overline{\overline {A.B}}$ = A.B