Question

In a CE transmitter amplifier, if the amplification factor is 150 and the collector voltage is 4 V and resistance is 2 kΩ, what should be the value of RB, given that the dc base current is 10 times the signal current?

(a) 5 kΩ

(b) 10 kΩ

(c) 15 kΩ

(d) 20 kΩ

This question was posed to me in exam.

This intriguing question comes from Transistors in portion Semiconductors of Engineering Physics II

Answer 1

Right answer is (d) 20 kΩ

Best explanation: Here, the output voltage is 4 V.

So, ic = 4/2000

= 2 mA

The signal current through the base, IB = ic/β

= 0.013 mA

The dc base current = 0.13 mA

Assuming here, that VBE = 1.4 V, we get

RB = (4.0-1.4)/0.13

= 20 kΩ.