audio amplifier

Discussion in 'Homework Help' started by salmanshaheen_88, Mar 30, 2010.

  1. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    anyone can give me audio amplifier circuit using transistor (Pnp or Npn), plz indicate the values of components as well
     
  2. bertus

    Administrator

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  3. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    I don't need such info, plz help me I am very frustrated with this project
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Show us what you got.
    That way we can help you.

    Bertus
     
  5. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Look at all PNP audio power amplifier.
    And we don't use workbench here. Post your diagram in PNG or JPG.
     
    Last edited: Mar 30, 2010
  7. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    here is the circuit 4.JPG

    the problem is that the output signal is not amplifying, it has same amplitude as input signal
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    "And we don't use workbench here" What do you mean by that? Every member in this forum is free to use the tool he/she prefer. I use Altium Designer.
     
  9. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    if you don't use workbench then make this circuit in altium and analyze it
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    Your extremely simple circuit is missing a speaker. So it has no power supply and has no load. Connect an 8 ohm speaker in parallel with the oscilloscope and see what happens.
    The speaker and the second transistor will get hot.
     
  11. salmanshaheen_88

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    Mar 5, 2009
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    I have used signal generator instead of microphone and oscilloscope instead of speaker
     
  12. bertus

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    Hello,

    An osciloscope has most times an input resistance of 1 M or higher.
    You are testing the circuit with this resistance.
    Try a resistor of 1K accross the inputs of the scope and see what happens.

    Bertus
     
  13. t06afre

    AAC Fanatic!

    May 11, 2009
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    I think then OP say a scope he/she is refering to a virtual scope in the software;)
    Edit: I also think the OP should apply some voltage to the transistor base bias network. Something is wrong with the schematics
     
  14. hobbyist

    Distinguished Member

    Aug 10, 2008
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    According to your schematic.


    Your osciloscope is being used as a series resistance from the positive battery terminal. So you have no positive supply to the circuit itself.

    The osciloscope needs to be connected to ground and one terminal to the collector of the transistor stage,

    You need to put a collector resistor in the collector loop, or you will not develop a voltage at the output with no collector resistor.

    Essentialy what your reading is the signal itself coming through the top resistor from the signal generator. Bypassing the trasnsistors all together.

    Here is how to hook up the oscilloscope for input and output readings with respect to a common signal ground.

    With no load.

    osc.jpg
     
    Last edited: Mar 30, 2010
  15. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    thank you soo much Hobbyist now the only problem left is that my signal at channel B is not amplifying, I mean its amplitude is same as the signal at channel A, how I should increase the amplitude of the output signal???
     
  16. hobbyist

    Distinguished Member

    Aug 10, 2008
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    Here is your circuit, with the same values you used, note the 10 ohm collector resistor, and all the settings on the osciloscope, and functrion generator. As well as the circuit configuration.

    osc 2.jpg
     
  17. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    hats off to you, im very happy from you.
     
  18. Audioguru

    New Member

    Dec 20, 2007
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    Notice that the extremely simple class-A "amplifier" has a voltage gain of only 10.
    If you use a microphone then you must add a preamp with a voltage gain of about 20.
     
  19. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    ok one more question if you can see in the diagram the input signal and output signal are out of phase, what should i do to make the phase of both the signals same???
     
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  20. salmanshaheen_88

    Thread Starter Active Member

    Mar 5, 2009
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    hey guru I have to show the waveform first to my professor and then my job will be to implement this circuit on bread board and I will have to use mic as input signal and speaker as output, so tell me how many ohms speaker I should select and which type of mic???
     
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