class B and AB idle current - diyAudio
 class B and AB idle current
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 6th October 2004, 02:55 AM #1 diyAudio Member   Join Date: Apr 2004 Location: BC class B and AB idle current would anyone be able to explain to me what the idle current for class b and ab are??...i understand that for class a it is 1/2 of Ipeak..how do you calculate for b and ab??...any help would be appreciated
 6th October 2004, 04:17 AM #2 diyAudio Member   Join Date: Jul 2004 Location: b Class AB is 5~20mA(Ie) from experience......
 6th October 2004, 04:37 AM #3 diyAudio Member   Join Date: Sep 2004 Location: Lansing, Michigan The simple answer is that you want to bias the output devices on just enough to eliminate the crossover distortion.
 6th October 2004, 04:53 AM #4 diyAudio Member     Join Date: Jun 2002 Location: Left Coast D. Self has done some work which seems to say that the voltage across the Vbe multiplier is what should be measured for least crossover distortion rather than current. ~2.89V for a EF output stage and 1.29V for aCFB configuration. Of course the best solution, not available to many DIYers is to adjust it for minimal distortion.
 6th October 2004, 04:58 AM #5 diyAudio Member   Join Date: Aug 2004 Location: Behind you For class B, quiescent current is ideally 0, but in reality will be bsomething very small. Class AB is anything greater than class , but less than the maximum peak load current. More than that is class A. You should note that the optimum bias current for minimum distortion is in class B, just below class AB. i.e. you should set the bias as high as possible without the devices conducting significantly. The reason for this is well described here. __________________ https://mrevil.asvachin.eu/
 6th October 2004, 05:32 AM #6 diyAudio Member     Join Date: Jul 2003 Location: berkeley ca It has been found by myself, that running as much current as possible without overheating is usually the best. If you want to get the best transisiton between class A and class B, which almost always is necessary, then with output bipolar transistors, drop 15mV-22mV across any emitter resistors. This is a good first approximation.
 6th October 2004, 06:14 AM #7 diyAudio Member   Join Date: Apr 2004 Location: BC thanx for your help guys

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