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NPN PNP coupling capacitor

Discussion in 'General Electronics Discussion' started by michael1978, May 3, 2018.

  1. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    Hi, can somebody explain me how this circuits works? please, i dont understand input capacitor and C2 and C3. Thanks I DONT UNDERSTAND COUPLING.png
     
  2. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    Hi i know input is input, and pnp emitter is to ground, but this C2 make it complicate for me.
    so i ask with little words how does work?
     
  3. duke37

    duke37

    5,211
    718
    Jan 9, 2011
    What is the pupose of the circuit?
    It looks to me to be a RF amplifier with Q! setting the current through Q2. The capacitors are to bypass RF current so to smooth the supply.
    What are the component values?
     
  4. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    Hello, Duke, sorry for late answer, this is an form of bisasing on RF DESIGN
     
  5. AnalogKid

    AnalogKid

    2,297
    646
    Jun 10, 2015
    Q1, R1, R2, and R5 form a constant current source to bias Q4 into its linear operating region without lowering the circuit's input impedance. C2 and C3 are bypass/decoupling capacitors to prevent the input RF signal from modulating the bias current and possibly forming an oscillator.

    ak
     
    Last edited: May 7, 2018
    michael1978 likes this.
  6. michael1978

    michael1978

    388
    2
    Mar 17, 2012
    Thanks a lot man , now i understand.
     
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