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Power gain

  1. Jan 28, 2014 #1
    An amplitude of output voltage Vo of a voltage amplifier was compared to the amplitude of input voltage Vi. The ratio Vo/Vi was 200.

    Find the power gain in dB.

    Can someone explain to me how to find this? The solution is given as below, but I don't understand how can Po/Pi = 200^2
     

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  3. Jan 28, 2014 #2

    rude man

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    Power goes as the square of voltage, assuming equal resistances: P = V^2/R.
    The solution is correct.
     
  4. Jan 28, 2014 #3
    Ah, I got it. There's another subquestion that I really don't understand. It says to find the output voltage when Vi is -6 dBV. I don't understand the solution. If Vo is 200 times larger than Vi, then how come Vo = 40 dB?
     

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    Last edited: Jan 28, 2014
  5. Jan 28, 2014 #4
    Disregard my question. I have understood it :)
    The solution seems to be written in a descending order.
     
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