# Bandwidth

Discussion in 'Homework Help' started by chaosweapon, May 3, 2009.

1. ### chaosweapon Thread Starter Member

Nov 14, 2008
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How do I calculate the bandwidth of a class A amplifier (CE-CE-CC)? Shouldn't it be dependent on the capacitors used?

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Yes in part.

One needs to set up & analyze a model (or models) which take account of the low , mid band and high frequency ranges.

Any semiconductor textbook worthy of its purchase price will discuss this in detail.

Otherwise visit a library with a good technical section or Google & evaluate the information.

3. ### PRS Well-Known Member

Aug 24, 2008
989
36
The response, Vo/Vi , if discreet capacitors are used, will be 0 at DC, but as the frequency increases the gain increases to its midband level where it stays until it reaches a point where it rolls off and falls to 0 again. The latter part or the curve is due to small capacitances within the device and any stray capacitance present.

The technique for determining the roll off point is to look at each source of capacitance and using the resistance it sees to compute its roll-off or roll-on point.
f=(1/2*pi*R*C). More help if you need it.

4. ### chaosweapon Thread Starter Member

Nov 14, 2008
15
0
Ok, I realized that I have to plot a graph of Gain versus frequency to find the bandwidth. Thank you for your help.

5. ### Ron H AAC Fanatic!

Apr 14, 2005
7,018
682
All the world hates a nitpicker, but I'm gonna do it anyhow:

f=1/(2*pi*R*C).

Placement of the parentheses is important!

6. ### PRS Well-Known Member

Aug 24, 2008
989
36
You're right, Ron. I'm so sorry.