1

### NEET 2013 (Karnataka)

The output from a NAND gate is divided into two in parallel and fed to another NAND gate. The resulting gate is a A
AND gate
B
NOR gate
C
OR gate
D
NOT gate

## Explanation

C' = $\overline {A.B}$

$\Rightarrow$ C = $\overline{\overline {A.B}}$ = A.B

Hence the resultant gate is AND gate.
2

### NEET 2013

In a n-type semiconductor, which of the following statement is true.
A
Holes are minority carries and pentavalent atoms are dopants.
B
Holes are majority carries and trivalent atoms are dopants.
C
Electrons are majority carries and trivalent atoms are dopants.
D
Electrons are minority carriers and pentavalent atoms are dopants.

## Explanation

In n-type semiconductor, electrons are majority charge carriers and holes are minority charge carriers and pentavalent atoms are dopants.
3

### NEET 2013

In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and current gain 20, the voltage gain will be
A
${1 \over 3}G$
B
${5 \over 4}G$
C
${2 \over 3}G$
D
1.5G

## Explanation

Formula for trans conductance $g$m is

$g$m = ${\beta \over {{r_i}}}$

Formula for voltage gain A,

A = $\beta$${{{R_L}} \over {{r_i}}}$

$\Rightarrow$ A = $g$mRL

Given A = G

$\therefore$ G = $g$mRL

$\Rightarrow$ G $\propto$ $g$m

$\Rightarrow$ ${{{G_2}} \over {{G_1}}} = {{{g_{{m_2}}}} \over {{g_{{m_1}}}}}$

$\Rightarrow$ G2 = ${{0.02} \over {0.03}}$ $\times$ G = ${2 \over 3}G$
4

### 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) · C

So it is clear that Y = 1, when A = 1, B = 0 and C = 1