Electronics and Communication Engineering - Exam Questions Papers - Discussion

19. 

Consider the common emitter amplifier shown below with the following circuit parameters: β = 100, gm = 0.3861 A/V, r0 = ∞ rp = 259 Ω, Rs = 1 kΩ, RB = 93 kΩ, RC = 250 Ω, RL = 1 kW, C1 = ∞ and C2 = 4.7mF.

The resistance seen by the source Vs is

[A]. 258 Ω
[B]. 1258 Ω
[C]. 93 kΩ
[D].

Answer: Option B

Explanation:

Zs = Rs + (RB || Brs)

rc = 2.475 = 1.258 kV


Gopal said: (Sep 19, 2016)  
Rpi = bita/gm = 100/0.3

so, rb/rpi = rc.

Vinay said: (Mar 10, 2017)  
Could you explain, please.

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