Amplifier designing with 6 desired properties

Discussion in 'Homework Help' started by kmkl, Dec 29, 2010.

  1. kmkl

    Thread Starter Member

    Dec 29, 2010
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    1-) Ri:100kohm
    2-) Ro:1kohm
    3-) output power: 15w
    4-) gain: 60dB
    5-) THD < %5
    6-) Bandwidth: 100Hz-100KHz

    (allowed parts: R, L, C, Bjt, Opamp, Power transistors as many as you want)

    i know it is difficult. but it is my vital homework ever. ANY help, ANY clue will be appreciated. thank you.
     
    Last edited: Jan 10, 2011
  2. kmkl

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    Dec 29, 2010
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    :confused: :confused:
    which part should i start with....?
    or, which property should i provide firstly?...
     
  3. Jony130

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    Feb 17, 2009
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    First you should start form pickup the right diagram.
     
  4. kmkl

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    Dec 29, 2010
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    it looks too complicated for me, cant we realize that with more simple circuit ?
     
  5. Jony130

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  6. kmkl

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    Dec 29, 2010
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    thanks for your help and interest. my teacher said about the homework that,
    "it is easy, except 20w power at Ry it can be implemented with only 2-3 stage transisor.
    to suply power, you should add some power transisors parallel to Ry"

    and the matter is, i am not good at this lesson, and i cant do it on my own. :(
     
  7. Jony130

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  8. kmkl

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    Dec 29, 2010
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    yes it is but still too complicated. at least for me.
     
  9. kmkl

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    Dec 29, 2010
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    the output impedance is desired <0.25ohm.. is it possible?
     
  10. Jony130

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    So what type of a amplifier you are familiar with?

    Yes, if you use a large amount of a negative feedback
     
  11. kmkl

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    Dec 29, 2010
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    i can only understand from simple bjts. here is the project i am trying to complete.
     
    • ccc.pdf
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  12. Jony130

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    Hmm, so maybe this diagram
     
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  13. kmkl

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    Dec 29, 2010
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    well, what about the values ?
     
  14. Audioguru

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    Dec 20, 2007
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    If you don't know how to calculate the values of the extremely simple power amplifier then you should repeat (fail) the course.

    Whe did your extremely simple preamp have capacitors with a value of 10000000000uF?
     
  15. kmkl

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    Dec 29, 2010
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    i just need to do this homework.
     
  16. kmkl

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    Dec 29, 2010
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    i managed to adjust gain and bandwidth on "Vp", but when i add power transisors, everything loses up. and gain falls to -50dB.. whats wrong :confused::confused:
     
  17. Jony130

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    Well, Q4 is off (cut-of) all the time.
    And Q3 has small current gain so he heavily loads Q5 amplifier.
    And this is why voltage gain drop.
     
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  18. kmkl

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    Dec 29, 2010
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    i had tried to add an ab class power amplifier behind Vp, but output dc voltage were supposed to be 10v (vcc/2), but it is not too. is it because r9 is too small? how can i make that power bjts work ?
     
  19. Jony130

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    Maybe becaues you forgot to add capacitor between output stage and R9.
    [​IMG]

    And by the way, you need power supply voltage to be grater then
    Vcc > 2 * √(2*Pout* Rload) = 25V
     
    Last edited: Dec 31, 2010
  20. kmkl

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    Dec 29, 2010
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    ok. i will add capacitor, there and then
    as i understand, all i have to do is to change V2 for arranging power to 20w,
     
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