1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Analysing Power Amplifier circuits-General discussion

Discussion in 'General Electronics Chat' started by fantabulous68, Feb 27, 2010.

  1. BrownOut

    BrownOut Banned

    Joined:
    Jun 10, 2009
    Messages:
    4,630
    Likes:
    60
    Location:
    Huntsville, Alabama USA
    Q1 & Q1 appear to be an attempt at a voltage reference to bias the current mirror composed of Q6 & Q7. I wouldn't guarantee it's performance, however.
     
    Last edited: Mar 5, 2010
  2. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    Can the i/p node be considered a virtual ground?
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,234
    Likes:
    641
    Location:
    Derbyshire, UK
    It can't be considered anything - it's not a working circuit. It looks like someone who didn't know anything about electronics saw a circuit once, and then tried to draw it from memory a week later. Where did it come from?.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0

    it came from a university website www.ee.ukzn.ac.za
     
    Last edited: Mar 5, 2010
  6. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    Another Circuit

    I welcome any views on this circuit....
     

    Attached Files:

  7. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    Please don't post anymore weird circuits.
     
  8. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    Alright, no more weird circuits....Im curious as to the effect of Q7-8 in the circuit?Does anyone know whats its purpose?
     
    Last edited: Mar 5, 2010
  9. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    Lol, what's a weird circuit? :D
     
  10. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Q7-Q8 is a darlington pair connected to the collector of Q3. In the case that Q3 conducts anything, Q7-Q8 slams the output drivers against the Vcc rail producing a square wave. If C3 is the right value then Q2 will try to cut off the base current to Q3 and it will be an oscillator but its stability depends on R7. If Q4 is the right geometry then it will provide some compensation to Q2. But Q5 and Q6 are a current sink and maximize the voltage gain of Q7 and Q8 so they provide the best possible square waves.
     
  11. mneary

    mneary New Member

    Joined:
    Feb 27, 2007
    Messages:
    4,502
    Likes:
    67
    Location:
    California USA
    Students often like to post jokes on the internet.
     
  12. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    In the previous "weird" "strangest" circuit ever lol, i had asked What does the circuit Q1-2 achieve?

    I got the response:

    So now i would like to know if the reference voltage circuit is better in the last circuit posted compared to the weird cct?
     
  13. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    Aren't you the least bit excited to see something "new" ( that's ironic seeing that it came from the 70's)?:D
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    I copied and pasted some comments about these weird circuits in this theread:

    "It's not a real design, various bits are missing and many of the values are completely wrong.
    It needs throwing away and starting from scratch.
    A recipe for disaster. It's more likely to cause a chain reaction self destruct.
    Looks rubbish to me?
    It is the strangest amplifier that I have ever seen.
    Where did you find this one?
    Like your previous circuit, it doesn't look like a complete working design, and this one even less so.
    It's still non-functional, nothing like a working amplifier.
    It looks like someone who didn't know anything about electronics saw a circuit once, and then tried to draw it from memory a week later."
     
  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,234
    Likes:
    641
    Location:
    Derbyshire, UK
    Yes, this is yet another total piece of rubbish - no wonder you never hear of amplifers made in South Africa.

    None of the 'designs' you've posted would work - they are just rubbish, and bear little resemblance to anthing that would.
     
  16. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    I know it doesn't work.

    I just found it funny how you labled it a weird circuit. :D
     
  17. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    I'm young and inexperienced..........I'm just trying to understand power amplifier ccts and get views...........i don't know what I post works or not....and that's why i welcome any views....
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,234
    Likes:
    641
    Location:
    Derbyshire, UK
    Read the free book you downloaded here.
     
  19. BrownOut

    BrownOut Banned

    Joined:
    Jun 10, 2009
    Messages:
    4,630
    Likes:
    60
    Location:
    Huntsville, Alabama USA
    In your last circuit, there was a voltage reference made form Z1 & Q1, which might be the only functional part of the design. But it has no compensation for temperature.
     
  20. fantabulous68

    fantabulous68 Member

    Joined:
    Feb 20, 2007
    Messages:
    323
    Likes:
    0
    I tried downloading it MR Goodwin but it was corrupted and cant open up......................................

     
  21. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,234
    Likes:
    641
    Location:
    Derbyshire, UK
    I downloaded it last night (as it wasn't on my new computer), it worked absolutely fine - I suggest trying it again - do you have a slow connection speed?, and lot's of breaks in service?.
     

Share This Page