Hi
Somewhat fed up of the tiny audio output from my FM3,
I changed the emitter follower transistor configuration
that provides current gain, but no voltage gain, to a
self biased NPN stage for each channel, capacitively coupled with 22N
from the MC1310P output, 33k to the collector of a BC547 from R128, C121
and 430k from collector to base. then 330n output.
Pretty simple, provides perfect bias for the NPN base
and importantly maintains the nice FM3 audio quality
now with decent audio output.
Schematic attached.
Cheers / Chris
Somewhat fed up of the tiny audio output from my FM3,
I changed the emitter follower transistor configuration
that provides current gain, but no voltage gain, to a
self biased NPN stage for each channel, capacitively coupled with 22N
from the MC1310P output, 33k to the collector of a BC547 from R128, C121
and 430k from collector to base. then 330n output.
Pretty simple, provides perfect bias for the NPN base
and importantly maintains the nice FM3 audio quality
now with decent audio output.
Schematic attached.
Cheers / Chris
Adding emitter resistance and for that matter base resistance to ground
yes would improve stability.
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