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What is the most simple PA?

Discussion in 'General Electronics Discussion' started by rogerk8, Sep 20, 2013.

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  1. rogerk8

    rogerk8

    176
    0
    Jul 28, 2011
    Hi!

    I wonder how to build a very simple power amplifier.

    I would prefere to build it with descrete transistors.

    But how would my attached amplifier sound?

    Best regards, Roger
     

    Attached Files:

    • Amp.PNG
      Amp.PNG
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  2. davenn

    davenn Moderator

    13,894
    1,969
    Sep 5, 2009
    hey Roger
    havent seen you for a while

    I think you will find there's a little more circuitry involved for a push-pull arrangement

    have a look here for an example

    typing discrete transistor amplifier circuit " into google images comes up with quite a few ideas


    DAve
     
  3. rogerk8

    rogerk8

    176
    0
    Jul 28, 2011
    Hi Dave!

    Well I've been stuck at physics forum.

    Today I however got banned.

    Talked too much sex in my "Why do we need a spouse"-thread.

    I'm just laughing at it because how could you seriously not discuss sex in such a thread?

    Anyway, I am banned until 30/9 :)

    Take care Dave and thank you for your tip!

    Best regards, Roger
     
  4. rogerk8

    rogerk8

    176
    0
    Jul 28, 2011
    What is actually the problem with my drawing?

    I mean, the OP will compensate for the unlinearities, will it not?

    I think it is as simple as it can be.

    Even though you still need some cooling arrangement (at least for higher output power).

    Best regards, Roger
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,500
    2,840
    Jan 21, 2010
    Theoretically, yes.

    Practically, no.

    The smaller you can make those non-linearities the better.

    Biasing the transistors so they're always slightly on is one way to do this.
     
  6. rogerk8

    rogerk8

    176
    0
    Jul 28, 2011
    Hi!

    I have now designed a bridge-coupled version of the above for car usage.

    Doing the math I did however become disappointed of the fact that power output would be less than some 12W in 4 Ohm speakers. This while using Darlingtons as power BJT's. But this is almost neccesary if you want to use a standard OP which seldom can supply more than some +/-10mA. And while standard power BJT hfe is around 50 only, this would result in 500mA at output only.

    A way around this would be to use a high output current OP (along with ordinary BJTs). But they might not be available as rail-to-rail also, so the benifit kind of disappears.

    I say that my picture below is about the simplest way to design a car power amplifier without too much distorsion. Am I right?

    Best regards, Roger
     

    Attached Files:

  7. rogerk8

    rogerk8

    176
    0
    Jul 28, 2011
    Hi!

    It struck me that the above amplifier has to be revised regarding bias.

    I have now designed a complete "Car Amplifier" which should take care of these problems.

    My only wish now is that I could find a dual J-FET rail-to-rail OP. But in the mean time TL072 will suffice (highest SR of the J-FET TL0x2-series).

    I think I will actually build this amplifier just to test the "bad" sound of the unlinearities :)

    Best regards, Roger
     

    Attached Files:

    • KCA.PNG
      KCA.PNG
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