BJT Amplifier

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

  1. RSA_alan

    Thread Starter New Member

    Mar 22, 2014
    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

    I don't know where to start with a circuit like this.
    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
    Last edited: Mar 22, 2014
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    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.:)

  3. LvW

    Active Member

    Jun 13, 2013
    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......