Class AB amp DC bias adjustment - diyAudio
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Old 30th May 2012, 02:18 AM   #1
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Join Date: Jun 2011
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Default Class AB amp DC bias adjustment

guys,

I have PPI amp and I think it is class AB. When I replaced the BJT transistors with its correct part number I notice 1 of the 4 channels has a minimum of 200mV voltage on emitter to emitter even I rotate the potentiometer into minimum- I dont know if it called DC offset or DC bias voltage?

Here are my questions what should be the voltage on across resistor between emitter terminals? How about across speakers terminals?

Do you think it is acceptable to pass this amp with a minimum setting of around 200mV across resistor? Any idea?


thank you guys! more power!
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Old 30th May 2012, 02:31 AM   #2
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Emitter to emitter is bias voltage. At that voltage, I'd expect that the output transistors would be overheating within a few seconds.

DC offset is measured across the speaker terminals for the channel being tested.
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Old 30th May 2012, 03:22 AM   #3
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Quote:
Originally Posted by Perry Babin View Post
Emitter to emitter is bias voltage. At that voltage, I'd expect that the output transistors would be overheating within a few seconds.

DC offset is measured across the speaker terminals for the channel being tested.
thank you perry! as your usual help...
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