Consider an amplifier circuit, where in a transistor is used in common emitter mode. The change in collector current and base current respectively are 4 mA and 20 UA when a signal of 40 mV is added to the base-emitter voltage. If the load resistance is 10 k 2, then power gain in the circuit is 

Options

A. `1xx10^(4)`
B. `2xx10^(7)`
C. `8xx10^(5)`
D. `1xx10^(6)`

Answer

B

Explanation

`R_(L)=10xx10^(3)Omega,DeltaI_(c)=4xx10^(-3)A,DeltaI_(B)=20xx10^(-6)`
`A,V_(BE)=40xx10^(-3)V`
Power gain `=beta^(2)R_(L)//R_(B)`
`=((DeltaI_(c))/(DeltaI_(B)))^(2).(R_(L))/(R_(B))=((DeltaI_(c))/(DeltaI_(B)))^(2)xx(R_(L))/((V_(BE)//DeltaI_(B)))`
`=((40xx10^(-3))/(20xx10^(-6)))^(2)xx(10xx10^(3))/(40xx10^(-3))xx20xx10^(-6)`
`implies" "A_(P)=2xx10^(-7)W`