Can someone teach me how to calculate the bandwidth of a cascaded bjt amp?

Question

Can someone teach me how to calculate the bandwidth of a cascaded bjt amp?

Answer 1

If you have an oscilloscope or similar measuring tool, you can do this:

1. Measure the maximum amplification that you can achieve

2. Divide this number by sqrt(2)

3. Find two frequencies, one low and one high, at which the amplification is equal to the answer in step 2

4. The bandwidth is the distance between the two frequencies measured in step 3.

If it's just a diagram and you need to use math, then you'll have to use the BJT equations to calculate the maximum gain for step 1 and low/high frequencies for step 3.  You'll have to use the exact formulas (ones with exponentials) and not the simplified ones because otherwise you'll get a pretty big error.