# Circuit analysis help

Discussion in 'Homework Help' started by MOS.EE, Apr 21, 2013.

1. ### MOS.EE Thread Starter New Member

Apr 21, 2013
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I need help figuring out the lower and upper -3dB frequencies of the amplifier below. I must keep the answer in terms of the circuit components shown and the transistor gm, ro, Cgs and Cgd. Assume Cin >> Cgs, Cgd.
I must also consider channel length modulation.

power supplies: VDD = +5V, VSS = -5V
transistors: Vtp = Vtn = 0.3V and (k'W/L)p = (k'W/L)n = 1mA/V2

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2. ### WBahn Moderator

Mar 31, 2012
18,088
4,917
You need to show your best attempt at a solution (remember, it is YOUR homework, after all). We will then be happy to help steer you in the right direction.

This is not the Homework Done For You forum.

3. ### MOS.EE Thread Starter New Member

Apr 21, 2013
9
0
Well with this problem i'm not exactly sure where to begin. I know I should plot the pole against the gain. I was going to use the equation f = 1/2*pi*RC for the pole or frequency response, and find the total resistance for R, but i'm not sure if this is a good method for solving the problem.

4. ### WBahn Moderator

Mar 31, 2012
18,088
4,917
Isn't the first step in analyzing these circuits usually finding the small signal equivalent circuit?

5. ### MOS.EE Thread Starter New Member

Apr 21, 2013
9
0
I'm guessing you mean its T equivalent? Yes, I solved for that and from there I could probably find the gain and frequency, but i'm not sure what to do after I have those as far as finding the lower and upper -3db limits

6. ### WBahn Moderator

Mar 31, 2012
18,088
4,917
Well, our crystal balls aren't good enough to see your work unless you post it. For frequency response questions, the pi model is usually more useful, but that's not a blanket statement.