Audio Systems: what the class (A,B,AB,C,D,G,H,S) mean in power amplifier ?, rf amplifier, crossover region

Question
hello,
i just want to know that in power amplifier specified that this power amplifier is "H" class? please explain how these class are determined and give detail of every class power amplifier efficiency in percentage out put. example i had heared that "A" class power amplifier less efficient and "AB" class amplifier upto 75% efficient. power amplifier means it used in dj system.

Answer
There is no specific efficiency for a give class because there are variations in the biasing levels.  But, in general, class A is the less efficient.

Please google for the class you are interested in as there are good lectures for each class.

A: full bias, least efficient of the push-pull type circuitry.
B: bias set for full switching between push-pull outputs.  Efficient for distortion is high.
AB: a bias in between A and B, bias is set for best distortion during crossover region of push = pull output.
C: Bias is less than full conduction. Not used for audio.
D: Switching class.  Can be very high efficiency but it depends on circuitry.
G & H: are variations on AB with the added feature of the magnitude of the rails ability to slide up and down in voltage.


Here is a pretty good wrap up or summary of the various types.

http://electronicdesign.com/analog/understanding-amplifier-operating-classes#cla

S class:  Is an RF amplifier and uses high frequency switching. It can theoretically reach 100% efficiency. It is used primarily in the mobile radio field for base station application.  You can read about it in some detail here:

http://www.imws.nuim.ie/publications/documents/sralph.pdf

I don't understand your dj comment as audio frequency amplifiers are most always class AB or some variation of it.  The Class D type are frequently used in portable and mobile applications where lots of power is needed with little space to mount the electronics and low heat generation.  Class D can be 90% to 95% efficient.  The downside of Class D is that it generates lots of rf energy caused by the switching frequencies employed.

And, you can google getting further technical information on your own.

Best wishes.  Hope this is helpful for your clear understanding.