Jim Thompson wrote:

Jim Thompson wrote:
Jim Thompson wrote:
"colin" wrote:
"Winfield Hill" wrote
Eeyore wrote...

In response to various posts please find attached a mic amp
which has seen volume production in commercial equipment.

Feel free to ask any questions / criticise whatever.

It's nice to see the diff-pair currents going directly to
the output opamp, with it's 6.8k resistors. But why'd ya
steal away loop gain so aggressively by choosing 680-ohms?

Now theres no resistors, the diff voltage input to the op amp is always
zero,
so theres no diff voltage accross the 680r so they dont have an effect on
diff voltage.

Sno-o-o-orkle! Does not!

...Jim Thompson

Not clear speech... Does not have any effect.

...Jim Thompson

Damn. I still can't say it right.

The 680 ohm resistors don't affect gain to the output (from the
input), but they do affect the OpAmp loop-gain operating point.

How ?


I wonder what stability, and possibly distortion effects, result?

...Jim Thompson

None.

Graham