Connect with us

POWER AMPLIFIERS

Discussion in 'Electronic Basics' started by Paul Burridge, Dec 1, 2005.

Scroll to continue with content
  1. Oh please do. We don't get unsolicited lectures very often. ;-)
     
  2. techpro

    techpro Guest

    an amplifier circuit which uses power transistor is called power
    amplifier .the are classified based on conduction angle.there are four
    categorizes of power amplifiers they are
    class A- conduction angle 360degrees
    class B-conduction angle 180degrees
    classC-conduction angle less than 180degrees
    classAB-conduction angle more than 180 degrees
    further classA is classified into
    1.series fed class A power amplifier .
    2.transformer coupled class A power amplifier.
    SERIES FED CLASSA
    it is called series fed because output is connected in series.
    advantages
    *the output signal is the exact replica of the input signal and has
    less distortions.
    disadvantages
    *it has very less efficiency and has maximum efficiency of 25%.
    the efficiency is less because in circuit we have resistor at collector
    of transistor due to voltage drop across this resistor we have less
    efficiency.
    to overcome this disadvantage we go for transformer coupled classA
    where we use transformer in place of resistor of seriesfed due to which
    voltagedrop reduces and efficiency increasesand it has a maximum
    efficiency of 50%.
    I would like to discuss this topic later.
     
  3. techpro

    techpro Guest

    thank u,
    i am new to this group ,i would like to know about this topic.if u know
    any references please forward .
     
  4. techpro

    techpro Guest

    as discussed earlier we use transformer in place of resistor to improve
    efficiency.the other additional advantage is impedance matching .
    impedance matching can be achieved because the transformer has primary
    and secondary windings .by adjusting the values of the resistors placed
    at input and output say R and R1 the ratio of windings can be achieved
    as it depends on the following relation,i.e
    R=R1(N\N1).
    where N and N1 are primary and secondary windings.
    disadvantage
    a)the output signal is distorted as id contains
    1.)harmonic distortation.
    this is due to nonlinearities present is transistor or active
    devices(BJT,FET,etc)
    2.)phase distortion.
    this is due to mismatch of phase angle.
    3.)frequency distortion.
    this is due to difference in frequency at input and output.
    b)less efficiency
    To over come these disadvantages we go for CLASS B
    power amplifier.
     
  5. PeteS

    PeteS Guest

    ---Rest of self serving lecture snipped-----

    For want of a better term, you are full of Excrement of Male Bovine
    (EoMB, as suitable acronym).

    With credits and apologies to Tim Bray as original author of the term.

    Perhaps your pixel persona might better be techdoh.

    Cheers

    PeteS
     
  6. PeteS

    PeteS Guest

    Interestingly, this looks suspiciously like a Q&A session from a basics
    book ;)

    Cheers

    PeteS
     
  7. Guest

    Just go BUY one you like and have a Merry Christmas.
    GG
     
  8. techpro

    techpro Guest

    sorry,
    it was the basic knowledge wat i had in this topic .may be it was like
    ques and answer section but i felt that it can be disscussed better
    only this way,if any more idea please suggest.thank u.
     
  9. Transformer coupled amplifiers at audio frequencies are obsolete.

    Bridge-tied amplifiers are worth looking at as are Class D amplifiers, if
    you are after the best efficiency possible.

    If you are into linear stuff, the Class AB types with heavy negative
    feedback and current limiting are good.
     
  10. Bob Myers

    Bob Myers Guest

    Nope; a "power amplifier" is either (a) an amplifier which
    is used to obtain a significant gain in power, output vs. input
    or (b) more colloquially, the output stage of a circuit, intended
    to deliver significant power into the load. Amplifiers are
    not classed by the type of devices from which they are
    constructed. (I take it the finals at our old college radio
    station wouldn't have been considered "power amplifiers"
    per the above, since they used tubes rather than "power
    transistors"? :))
    Nope; AB is more than 180 BUT LESS THAN 360;
    you can't forget that final qualifier. And actually, the
    above classifications are not, strictly speaking, limited to
    "power" amplifiers (although they'd most often be seen in
    that context.
    Why would you think that only Class A amps can be
    distinguished in this manner?
    With what, Einstein?
    The goal of any amplifier (esp. all Class As), not a distinguishing
    characteristic.
    That max. efficiency is generic to Class As, too.
    OK - but find a better book to swipe your material from first.

    Bob M.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-