class ab amp

Discussion in 'General Electronics Chat' started by abdus, Jul 8, 2010.

  1. abdus

    Thread Starter New Member

    Mar 4, 2010
    22
    0
    i have found this ckt of class ab amp..
    i jst need some one to please confirm this ckt
    one problem is that i have seen almost all the amps that one input must b ground,,but here its not like that ,,,why?
    the link for this ckt is:
    http://mrcshobbies.blogspot.com/
    i have designed the one with 21w.(.according to my requirement..)
    please help
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    This is an AC amplifier and the input is capacitively coupled. That mans the DC level is set on the other side of the cap. I don't know why they return the input to the positive rail, but since it is capacitively connected to ground, it should work. I would return it to ground.
     
  3. dsp_redux

    Active Member

    Apr 11, 2009
    182
    5
    The upper rail becomes an alternative ground when doing an AC analysis. You can use it, but I prefer using ground instead.
     
  4. abdus

    Thread Starter New Member

    Mar 4, 2010
    22
    0
    ok...what about this one...if i use this amp instead of the last one,,then it will be good or not?
    http://www.redcircuits.com/Page1.htm
    this is the link..please help me to choose..
     
  5. abdus

    Thread Starter New Member

    Mar 4, 2010
    22
    0
    and in the link,,it also says that:
    "D1 must be in thermal contact with Q1."
    what dose that mean???:confused:
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    Thermal contact means that the body of D1 is touching transistor Q1.
    It is mounted body to body.
    You can use some thermal paste to have a good thermal bound.

    Bertus
     
  7. abdus

    Thread Starter New Member

    Mar 4, 2010
    22
    0
    so can u suggest me ,,that which circuit should i use for an amp?i mean which circuit u think is more accurate..?
     
  8. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    Thermally bonding D1 to Q1 improves the accuracy and response as both semiconductor devices have similar properties. If you only need a basic amp then this is unnecessary.
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    abdus likes this.
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