Small Signal Analysis-BJT/FET

Discussion in 'Homework Help' started by no12thward, Feb 22, 2011.

  1. no12thward

    Thread Starter Member

    Jan 10, 2011
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    Do the boxed values here seem to be correct for these 2 BJT and 1 FET circuits? Mainly the "Av" values I am concerned of. Is it supposed to be a negative number?
     
  2. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    9,459
    915
    Av is voltage gain, not a resistance.
    Ai is current gain, not a resistance.

    The transistor inverts the signal so the gains are negative.
     
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  3. no12thward

    Thread Starter Member

    Jan 10, 2011
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    0
    So the current gain would end up being negative as well, or just the voltage gain?
     
  4. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    As Audioguru said, get rid of those k and Ω suffixes on your Av, Ai, and Vo results. The gains Av and Ai are dimensionless ratios. Sometimes you will see Av specified like, for example, 100 V/V (volts per volt) for a voltage gain of 100, but the V/V units cancel so the result is really dimensionless.

    Also, on page 1/3, you have copied your Zo and Zi values from your calculations into the wrong boxes.
     
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