The input resistance of a common emitter transistor amplifer, if the output resistance is `500 K Omega`, the current gain `alpha = 0.98` and 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

(a) Apply the concept, power gain is product of current gain and voltage gain and find the resistance
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) [(500 xx 10^(3))/(R_(1))]`
Power gain `= 6.0625 xx 10^(6) = 49 xx [(500 xx 10^(3))/(R_(1))] xx 49`
`:. R_(1) = 198 Omega`