Why this amp does not function ????? - Page 2

azira · 23rd January 2004, 04:45 PM

First things first... the LM386 has internal feedback from it's output, it's not the best choice device for this kind of configuration. You're going to want some global feedback to help with the crossover distortion (but you won't get rid of it.. as I have recently learned).

Secondly... you've DC isolated the bases and the emitters of the transistors so they have no references at all. That is probably causing some problems. You need to reference the bases some how. Put something like 10k from the NPN base to the +Rail and the 10K from the PNP base to the -Rail. That will "bias" the bases at 1/2 VCC and give a reference. This will still be in the same class of output if you do this.

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23rd January 2004, 04:45 PM	#11
azira diyAudio Member Join Date: Dec 2003 Location: Near Seattle	First things first... the LM386 has internal feedback from it's output, it's not the best choice device for this kind of configuration. You're going to want some global feedback to help with the crossover distortion (but you won't get rid of it.. as I have recently learned). Secondly... you've DC isolated the bases and the emitters of the transistors so they have no references at all. That is probably causing some problems. You need to reference the bases some how. Put something like 10k from the NPN base to the +Rail and the 10K from the PNP base to the -Rail. That will "bias" the bases at 1/2 VCC and give a reference. This will still be in the same class of output if you do this.

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