Oznog
Active Member
Looking over the LM386, I don't see the best way to use this in a circuit and could use some help.
I have a system which has a single 12v supply and an audio signal limited to 0 to 5v since it goes through some digital pots for mixing various sources. That signal is biased to 2.5v, I don't have the exact amplitude, this will be determined by pot settings later. Obviously less than 5v pp.
Anyways, the LM386 is an amp but not an op amp. With the basic 20 gain circuit, the 2.5v bias means an output clipping far past the +12v rail. My first thought from an op-amp perspective is of course to put the inverting input on the 2.5v bias point, but the spec sheet says +/-0.4v is an absolute max input value. So I assume this means I will need to put the inverting to ground and capacitively couple the noninverting input? That will mean the input signal will be below ground for 1/2 the cycle- is this the intended operating mode?
Now what about the output biasing? It needs to bias to around 6v ideally, before the speaker coupling cap. Does the 386 do this automatically somehow or what? Or does the DC bias of the input just get multiplied by the gain and set the output bias from there? I don't see where this seems to be addressed in schematics.
I have a system which has a single 12v supply and an audio signal limited to 0 to 5v since it goes through some digital pots for mixing various sources. That signal is biased to 2.5v, I don't have the exact amplitude, this will be determined by pot settings later. Obviously less than 5v pp.
Anyways, the LM386 is an amp but not an op amp. With the basic 20 gain circuit, the 2.5v bias means an output clipping far past the +12v rail. My first thought from an op-amp perspective is of course to put the inverting input on the 2.5v bias point, but the spec sheet says +/-0.4v is an absolute max input value. So I assume this means I will need to put the inverting to ground and capacitively couple the noninverting input? That will mean the input signal will be below ground for 1/2 the cycle- is this the intended operating mode?
Now what about the output biasing? It needs to bias to around 6v ideally, before the speaker coupling cap. Does the 386 do this automatically somehow or what? Or does the DC bias of the input just get multiplied by the gain and set the output bias from there? I don't see where this seems to be addressed in schematics.