-The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value of CinM) for the circuit?
A) 6.2 pF
B) 15 pF
C) 1205 pF
D) 2410 pF

Question

-The transistor amplifier in Figure  has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value of CinM) for the circuit?
A) 6.2 pF 
B) 15 pF 
C) 1205 pF 
D) 2410 pF

Quizplus · Accepted Answer

The value of $C_{inM}$ for the circuit can be calculated by considering the input capacitance $C_{in}$ and the Miller effect on the capacitance $C_{bc}$. The Miller effect essentially multiplies the capacitance $C_{bc}$ by a factor related to the gain of the circuit, making it appear larger at the input. However, in this specific calculation for $C_{inM}$, the primary factor is the given input capacitance $C_{in}$, which is 1200 pF. The additional capacitances due to $C_{be}$ and the Miller effect on $C_{bc}$ are relatively small in comparison and would slightly increase the total input capacitance. Therefore, the closest approximation given the options is 1205 pF, indicating that the original $C_{in}$ is the dominant factor, with a small addition from the other effects.

-The Transistor Amplifier in Figure Has the Following Values