In common emitter transistor as shown in Fig., the `V_(BB)` supply can be varied from 0 V to 5.0V. The Si. Transistor has `beta_(ac)=250` and `R_(B)=100kOmega, R_(c)=1k Omega,V_(C C)=5.0V`. Assume that when the transistor is saturated, `V_(CE)=0V` and `V_(BE)=0.8V`. Calculate the minimum base current, for which the transistor will reach saturation. Hence, determine `V_(i)` when the transistor is 'switched on' find ranges of `V_(i)` for which the transistor is switched off and switched on.

Options

A. `10mu A`
B. `20 mu A`
C. `30mu A`
D. `40 mu A`

Answer

B

Explanation

At saturation, `V_(CE)=0V`
Given, `V_(CE)=0.8V`
`therefore V_(CE)=V_(C C)-I_(C)R_(C) rArr I_(C)=(V_(C C))/(R_(C))=(5V)/(1k Omega)=5mA`
`and I_(B)=(I_(C))/(beta)=(5mA)/(250)=20muA`