Thanks for the answers, Russell.
----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>

> You say 'amplify my mcu's output.
> What is the drive signal?
> What voltage swing open circuit?

Drive signal - AVR output pin.
Voltage swing - 5-0V = 5V

> Use an IC amp !!!!, but
> E&OE, typed on fly

Normally I would, but this is a Halloween project, that I don't have the
money, time, or interest to do "right." I'm just working with what I have on
hand.

> If you want a REALLY basic low power amplifier try this.
>
> 1.    If it is a full rail rail swing voltage but with high impedance, so
no
> power.
>
> 1 x npn
> 1 x speaker
>
> Base to signal source
> Collector to Vdd
> Emitter to ground.
>
> This has DC through speaker which is not nice :-)

I actually tried this already, but I'm not getting much volume out of the
speaker. I tried a couple of different base resistor values to make sure
that the transistor's saturating properly, but no joy.

> 2.    As above but add a 100uF or higher electrolytic and a resistor - say
> 100r to start
>
> Base to signal source
> Collector to Vdd
> Emitter to resistor to ground.
> Speaker bottom side to ground
> Speaker top side to capacitor negative terminal
> Capacitor positive terminal to emitter
>
> Vary 100r to see what difference it makes.

OK, I think I'll give this one a try... Sounds promising

Thanks again for the ideas.

- Robert

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