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Current draw question for amplifier

  1. Jan 15, 2010 #1
    I'm sure it will be easy for someone to answer. I have an amplifier circuit running in multisim and it's drawing around 9mA of current, 25VDC. Am I right in thinking that the circuit will only draw as much current as needed from the transformer, and a 25v 2A tranny would work to power the circuit? Just want to be 100% sure before I apply any power to the real thing.

    Thank you,
  2. jcsd
  3. Jan 16, 2010 #2


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    Science Advisor

    If you just have a simple amplifier with resistor loads for transistors, the current will not vary much from the 9 mA.

    If you are using an audio chip to drive a speaker, the current will vary depending on the audio drive level.
    If the quiescent current (with no input audio voltage) is only 9 mA then the full output current is probably less than an amp, so a 2 amp power supply would be OK.

    A 25 volts AC secondary transformer would not be used to generate 25 volts DC directly. If you rectified it and filtered it, the output would be about 35 volts.
    You could use this to give an input for a 25 volt regulator.
    To get 25 volts DC, you would need a transformer giving about 18 volts out.
  4. Jan 16, 2010 #3
    No audio chip. Just the resistor loads for transistors.

    Hadn't made it to the transformer voltage prior to rectification yet, thought that might be the case.

    Thank you!
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