In a common emitter transistor amplifier, the audio signal voltage across resistance of 1 k$\Omega$ is 2V. If the base resistance is 200$\Omega$ and the current amplification factor is 50, the input signal voltage will be

1. 4 mV

2. 8 mV

3. 16 mV

4. 32 mV

$\mathrm{If}<mspace\; width="1em"></mspace>\mathrm{\alpha }<mspace\; width="1em"></mspace>\mathrm{be}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{current}<mspace\; width="1em"></mspace>\mathrm{gain}<mspace\; width="1em"></mspace>\mathrm{of}<mspace\; width="1em"></mspace>\mathrm{a}<mspace\; width="1em"></mspace>\mathrm{transistor}<mspace\; width="1em"></mspace>\mathrm{in}<mspace\; width="1em"></mspace>\mathrm{common}<mspace\; width="1em"></mspace>\mathrm{base}<mspace\; width="1em"></mspace>\mathrm{mode}<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>\mathrm{\beta }<mspace\; width="1em"></mspace>\mathrm{be}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{current}<mspace\; width="1em"></mspace>\mathrm{gain}<mspace\; width="1em"></mspace>\mathrm{in}$
$\mathrm{common}<mspace\; width="1em"></mspace>\mathrm{emitter}<mspace\; width="1em"></mspace>\mathrm{mode}<mspace\; width="1em"></mspace>\mathrm{then}-$

1.  $\mathrm{\alpha }<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>1<mspace\; width="1em"></mspace>$

2.  $\mathrm{\beta }<mspace\; width="1em"></mspace>><mspace\; width="1em"></mspace>1<mspace\; width="1em"></mspace>$

3.  $\mathrm{\alpha }<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>\frac{\mathrm{\beta }}{1<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>\mathrm{\beta }}$

4.  All of these

The input resistance of a silicon transistor is

100 $\mathrm{\Omega }$. Base current is changed by 40 $\mathrm{\mu A}$

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$\mathrm{\Omega }$.

The voltage gain of the amplifier is

1. 2000

2. 3000

3. 4000

4. 1000

The device that can act as a complete electronic circuit is

1. Junction diode

2. Integrated circuit

3. Junction transistor

4. Zener diode

For transistor action:

Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)                                       
4. (c) and (d)