Question

What is the value of voltage VB of a CC amplifier configuration if VCC = 12V, R1 = 5kΩ and R2 = 8kΩ?

(a) 6.54V

(b) 0.7V

(c) 4.6V

(d) 7.38V

I had been asked this question in an online interview.

My doubt is from Simplified Calculations for the CC Configuration in portion Low Frequency Transistor Amplifier Circuit of Electronic Devices & Circuits

Answer 1

Correct option is (d) 7.38V

To explain I would say: The voltage VB of a simplified common collector amplifier configuration can be calculated using VB = I × R2. Given, VCC = 12V and R1 = 5kΩ and R2 = 8kΩ:

I = VCC / R1 + R2 = 12 / (5 + 8) = 0.92mA

VB = I × R2 = 0.92mA × 8kΩ = 7.38V