Finding the Gain

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

  1. DavS13

    Thread Starter New Member

    Jun 16, 2014
    21
    0
    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.

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  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    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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