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Capacitors in Common Emitter Amplifier Circuit ?

  1. Jan 5, 2009 #1
    Capacitors in "Common Emitter Amplifier" Circuit ?

    Should i use Capacitors in "Common Emitter Amplifier" ( CEA ) Circuit ?

    As i saw many CEA circuits designed without any capacitors there !

    And also hear that it's better to use two capacitors, one after the Voltage Source ( that feeds the Base ), And another Just before the another Voltage Source ( that feeds the Collector ).

    So, What do you think about that ? and why should is (use/don't use) them ?
  2. jcsd
  3. Jan 5, 2009 #2
    Re: Capacitors in "Common Emitter Amplifier" Circuit ?

    It will be better if you can provide a diagram.

    Let me guess. You are talking is the AC coupling cap. A transistor need proper biasing before it can work as an amplifier. The bias on the base might not be the same as the voltage source into the base. A cap will filter the DC from the voltage source so it does not affect the transistor biasing.
    An AC decoupling cap usually needed to couple the output signal from the collector of the transistor to the second stage amplifier also.

    This is my guess of your question without seeing the diagram. Hope that answer your question.
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