An n - p- n transistor is connected in common - emitter configuraration in which collector supply is 8 V and the voltage drop across the load resistance of ` 800 Omega ` connected in the collector circuit is 0.8 V . If current amplification factor is 25 , determine collector - emitter voltage and base current . If the internal resistance of the transistor is ` 200 Omega ` , calculate the voltage gain and the power gain.

Options

A. `5.2 V,1.86,3`
B. `6.2V,186,5.5`
C. `7.2 V,3.86,3.698`
D. `8.2V,4.91,3.15`

Answer

C

Explanation

The circuit arrangement is shown in figure

collector current `I_(C) =("Voltage drop across" R_(L))/(R_(L))`
`=(0.8)/(800) =10^(-3) amp`.
Now `V_(CE) =8-0.8 =7.2` volt
Current gain `beta =(I_(C))/(I_(B)) (or)(25)/(26)=(10^(-3))/(I_(B))`
`:. I_(B)=(26)/(25) xx 10^(-3) =1.04 xx 10^(-3) amp`.
Voltage gain = `beta (R_(L))/(R_(C))`
`= (25)/(26)xx(800)/(200) =(100)/(26) =3.846`
Power gain `= beta^(2)(R_(L))/(R_(C))=((25)/(26))^(2)xx(800)/(200)`
`= ((25)/(26))^(2)xx 4=3.698`.