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

Answer

A

Explanation

Voltage gain =`Av=betaR_o/R_i`
Also, current gain:`beta=alpha/(1-alpha)=0.98/(1-0.98)=49`
`A_V=(49)((500xx10^3)/R_i)`
Power gain= current gain x voltage gain
Power gain=`6.0625xx10^6=49xx((500xx10^3)/R_i)xx49`
or `R_i=198 Omega`