1
MCQ (Single Correct Answer)

AIPMT 2012 Mains

To get an output Y= 1 in given circuit which of the following input will be correct ?

A
A $$ \to $$ 1,  B $$ \to $$ 0,  C $$ \to $$ 0
B
A $$ \to $$ 1,  B $$ \to $$ 0,  C $$ \to $$ 1
C
A $$ \to $$ 1,  B $$ \to $$ 1,  C $$ \to $$ 0
D
A $$ \to $$ 0,  B $$ \to $$ 1,  C $$ \to $$ 0

Explanation



The Boolen expression for the given combination is

output Y = (A + B) ยท C

So it is clear that Y = 1, when A = 1, B = 0 and C = 1
2
MCQ (Single Correct Answer)

AIPMT 2012 Mains

The input resistance of a silicon transistor is 100 $$\Omega $$. Base current is changed by 40 $$\mu $$A which results in a change in collector current by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4 k$$\Omega $$. The voltage gain of the amplifier is
A
2000
B
3000
C
4000
D
1000

Explanation

Current gain ($$\beta $$) :

$$\beta $$ = $${{\Delta {I_C}} \over {\Delta {I_B}}}$$

= $${{2 \times {{10}^{ - 3}}} \over {40 \times {{10}^{ - 6}}}}$$ = 50

Voltage gain of the amplifier is

AV = $$\beta {{{R_L}} \over {{R_i}}}$$

= 50 $$ \times $$ $${{4 \times {{10}^3}} \over {100}}$$ = 2000
3
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

The figure shows a logic circuit with two inputs A and B and the output C. The voltage wave forms across A, B and C are as given. The logic circuit gate is
A
OR gate
B
NOR gate
C
AND gate
D
NAND gate

Explanation

The truth table is
The logic circuit is OR gate.
4
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

Transfer characteristics [output voltage (V0) vs input voltage (Vi)] for a base biased transistor in CE configuration is as shown in the figure. For using transistor as a switch, it is used

A
in region III
B
both in region (I) and (III)
C
in region II
D
in region I

Explanation

In the given graph,

Region (I) โ€“ Cutoff region

Region (II) โ€“ Active region

Region (III) โ€“ Saturation region

Using transistor as a switch it is used in cutoff region or saturation region.

Using transistor as a amplifier it is used in active region.

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