The input resistance of a common emitter transistor amplifier, if the output resistance is `500 kOmega`, the current gain `alpha=0.98` and the power gain is `6.0625 xx 10^(6)` is

Options

A. `198Omega`
B. `300Omega`
C. `100Omega`
D. `400Omega`

Answer

A

Explanation

Voltage gain, `A_(V)=beta(R_(2))/(R_(1))`
Also, current gain, `beta=(alpha)/(1-alpha)=(0.98)/(1-0.98)=49`
`A_(V)=(49)[(500xx10^(3))/(R_(1))]`
Power gain `=6.0625xx10^(6)=49xx[(500xx10^(3))/(R_(1))]xx49`
`therefore R_(1)=198Omega`