1
MCQ (Single Correct Answer)

NEET 2016 Phase 2

For CE transistor amplifier, the aufio signal voltage across the collector resistance of 2 k$$\Omega $$ is 4 V. If the current amplification factor of the transistor is 100 and the base resistance is 1 k$$\Omega $$, then the input signal voltage is
A
10 mV
B
20 mV
C
30 mV
D
15 mV

Explanation

Voltage gain, A = $$\beta {{{R_C}} \over {{R_B}}}$$ = $$100 \times {{2000} \over {1000}}$$ = 200

Also, A = $${{{V_0}} \over {{V_i}}}$$

$$ \Rightarrow $$ $${V_i} = {{{V_0}} \over A}$$ = $${4 \over {200}}$$ = 20 mA
2
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

If in a p-n junction, a square input signal of 10 V is applied, as shown,



then the output across RL will be
A
B
C
D

Explanation

Here P-N junction diode rectifies half of the ac wave i.e., acts as half wave rectifier.
During + ve half cycle Diode is forward biased output across RL will be

During –ve half cycle Diode is reverse biased output will not obtained.
3
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

Which logic gate is represented by the following combination of logic gates ?

A
AND
B
NOR
C
OR
D
NAND

Explanation

The Boolean expression of this arrangement is

Y = $$\overline {\overline A + \overline B } $$ = $$\overline{\overline A} + \overline{\overline B} $$ = A.B

Thus, the combination represents AND gate.
4
MCQ (Single Correct Answer)

AIPMT 2015

In the given figure, a diode D is connected to an external resistance R = 100 $$\Omega $$ and an e.m.f. of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the citcuit will be

A
20 mA
B
35 mA
C
30 mA
D
40 mA

Explanation

Potential difference across resistance R

= 3.5 – 0.5 = 3.0 V

Current in circuit, I = V/R = 3/100 = 30 mA

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