Finding the Gain

Discussion in 'General Electronics Chat' started by DavS13, Nov 20, 2014.

  1. DavS13

    Thread Starter New Member

    Jun 16, 2014
    Please explain how the gain of this CE-CC circuit is about 3.3, or R3/R1. No very brief answers please, I want to know how it works so describe in detail how you arrive at your conclusion.

  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    The right hand side of R1 is fixed at approximately 0.65V (the base-emitter voltage of Q1) Therefore, if the input on the left hand side of R1 is raised by 1V a current of 1mA (1v/1k) will be introduced through Q1. This 1mA current through Q1 will be "mirrored" by Q2 (this is a current mirror) causing a reduction in the voltage at the collector of Q2 of 1mA x 3k3 = 3.3V. The emitter of Q3 simply follows its base.
    Last edited: Nov 21, 2014
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