How to Set The Bias Voltage

** The usual value for a 1k potentiometer.

** Tape recorders use AC bias - amplifiers use DC. ** One sets the idle current flowing in the output devices to some nominal value ( like 20mA ) using the DC voltage drop across one of the emitter ballast resistors.

..... Phil

The bias is the mid point(called the Q point) in the operating range of the transistor... assuming class A.

if you search google for class A, load line, Q point, bias, etc... I'm sure you'll find plenty of info that can explain it much better than I can.

Essentially though what your trying to do is bias the transistor so that neither side of the ac waveform is being clipped on its peak. If you do it one way to much you'll completely cut off one side of hte waveform(if not more) and vice versa. (class AB, B, C, and D do this and essentially the degree determines the class).

In a class A though you do not want them clipped so you have to find that mid point. It will not hurt the transistor if its not biased properly in this case cause it dissipates maximum power when it is biased properly(or close to it).

So go ahead and play around with it. If you got an oscilloscope or sound card you can use it to see the effect of biasing it wrong.

AKA "Suicide Bias" ;-)

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
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Thanks for the info.

The schematic was in the Class B section of his book.

Maybe I just need a good third/fourth-year EE introductory text. Any suggestions?

Thanks,

Michael

On Jul 22, 7:43=A0am, snipped-for-privacy@gmail.com wrote: > On Jul 22, 7:26 am, "Jon Slaughter" wrote: >

Phil Allison gave you the correct answer. Why aren't you happy with it? BTW, ignore Jon Slaughter's 'method'. You'll end up with some very hot transistors that converted themselves from semiconductors to conductors.

G=B2

I didn't say I'm not happy with his answers. I want to understand more, is all. The whole biasing scheme is new to me.

Either way, I think I found a good text:

Michael

Thanks