Question

In a CE amplifier, the current gain is 80 and the emitter current is 9 mA. The base current is ______.

Options

• `1/81 "mA"`

• 8 mA

• `1/8 "mA"`

• `1/9 "mA"`

Answer 1

In a CE amplifier, the current gain is 80 and the emitter current is 9 mA. The base current is `bb underline(1/9 mA)`.

Explanation:

I_E = I_B + I_C

β = `(IC)/(IB)`

Rearranging for I_C:

I_C = βI_B

Substituting in I_E = I_B + I_C:

I_E + I_B + βI_B

I^E = I_B(1 + β)

I_B = `(IE)/(1 + β)`

I_B = `9/(1 + 80) = 9/81 = 1/9"mA"`

`1/9"mA"`