# BJT Amplifier

Discussion in 'General Electronics Chat' started by RSA_alan, Mar 22, 2014.

1. ### RSA_alan Thread Starter New Member

Mar 22, 2014
1
0
Hi Guys

I'm really hoping somebody can help me.

We have received the following circuit from out lecturer (see attached) and we need to calculate the resistor values to achieve the following goals.

1. Voltage gain with feedback should be 200 V/V
2. Open loop gain should be in excess of 20 000 V/V
3. Input resistance should be 1MΩ
4. Output resistance should be less than 100Ω
5. Input is a 1mV peak to peak

Do I start at the output? Input?

Any help I can get will be very much appreciated.

Ps I see R1 is 1kΩ the value for R1 is not given

• ###### BJT Amplifier.jpg
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2. ### ericgibbs AAC Fanatic!

Jan 29, 2010
2,595
393
hi Alan,
I would start at the front end, ie: the differential input.

Look over this 'eee' pdf, its referenced to an excellent book about electronics, also from a sunny RSA Univ doc.

E

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3. ### LvW Active Member

Jun 13, 2013
674
100
Alan, yes - as eric has recommended, you should start with the input resistance requirement (do you know the formula for the one-sided input resistance of a diffential amplifier?).
As a second step, this leads to some information about the maximum quiescent current through this stage.
Together with the given power supply you can find a reasonable range of values for R4......