1.

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

Answer» Correct Answer - A
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`


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