circuit modification and help needed

Discussion in 'Homework Help' started by InnocentOfTheWorld, Jun 27, 2011.

  1. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    dear friends,
    i am attaching my circuit made in proteus as an power amplifier of 8 watt and speaker 8 ohm as load,which should work in audible frequency range.
    My circuit contains only one capacitor tell me it's appropriate value and kindly after adjusting values do frequency and transient analysis on proteus. and tell me how to do these analysis on proteus. i did many times but they don't work i tried to adjust y-axis scale but i was unable to adjust it may be problem in my software :(
    and also tell will this circuit work for 8 watt?
    anyone reply
    if you have questions ask me
     
    Last edited: Jun 28, 2011
  2. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    waiting for answers
    i am also attaching picture
    have a look on it and tell me how to edit it

    amplifier.png
     
    Last edited: Jun 28, 2011
  3. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Bumping is NOT needed.
    This is an international forum, so responses can take hours to even days.
    Not all have proteus, so post the schematic as a .PNG over here.
    Then others can also have a look.

    Bertus
     
  4. simo_x

    Member

    Dec 23, 2010
    200
    6
    Is not a simulator which tells you if the circuit will work in our real world, but only your knowledge about electronics.
    However, why you are not planning to do it with operational amplifiers instead of using all these transistors?
     
  5. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    i want to design this at discrete level as it is my task
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    So, it is a homework assignment from your instructor or professor?

    I'll tell you one thing, your 2N4401 and 2N3906 transistors you are using in the output section will not be adequate for the current that you will need. 2N3906 transistors are rated for up to 200mA collector current maximum, but 100mA is more of a practical limit. If you want 8 Watts output power, you will need 1A current through an 8 Ohm load, which is 10x the practical limit of the 2N3906.
    The 2N4401 is better, but still woefully inadequate.
     
  7. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    here is a new design i tried to made although working on proteus and giving the output as i am not much experienced tell me if there is anything which needs to be modified for better results.also proteus files are provided.yes it is a home task

    P.S
    now used tip122 and tip127 in output stage


    8 watt.png
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
  9. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    identify different stages of audio power amplifier and tell me about it's functionality


    8 watt.png
     
  10. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    By now you should know the AAC forum policy. Post your work and efforts on solving your problem in order to receive any help.

    Can you identify any amplification modules in your schematic?
     
  11. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    yes at input it is common emitter amplifier
    and output is class ab amplifier
    i want to know about the intermediate stage and how current amplification is achieved in that part
     
  12. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Your schematics have a dark grey background and a grid all over them which makes them hard to read.
    None of the connections have a dot so where lines cross it is impossible to see if they are connected or not.
    Some of thye text is impossible to read.
     
  13. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    I merged the threads as they are about the same circuit.
    Please do not start new threads when the other one is still active.

    Bertus
     
  14. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
  15. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Most power amplifiers except yours are DC-coupled but have an input coupling capacitor.
    All power amplifiers except yours have DC and AC negative feedback.

    It would be useful for you to look at some power amplifier circuits found in Google.
     
  16. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    47
    1
    tell me how it amplifies current
     
  17. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Didn't you learn about transistors?
    The darlington output transistors have a current gain of at least 1000 times and typically 4500 times.
    The peak current in an 8 ohm speaker with 8W is 1.4A so the base current is only 0.3mA or less to 1.4mA.

    The first transistor has a current gain of a few hundred. I can't read its tiny blurry part number. I also cannot read its tiny blurry resistor values.
     
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