> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Dumitru Stama
> Sent: 04 November 2009 22:59
> To: Microcontroller discussion list - Public.
> Subject: [EE] Amplifying a PWM signal
> 
> Hi guys,
> i have a question. My PIC18F2520 is set up to output a PWM signal. I
> want to amplify the signal's current and feed it into a speaker.
> Right now using only a single PN2222A i can hear the sound but the
> volume is quite low.
> I tried a LM386 and the output is what i really want but only if i
> select the 200x gain schematics.
> I don't know what should i try now, i really want to use only simple
> components and not a dedicated amplifyer like LM386.

Something doesn't add up here, what supply is your PIC and LM386 running
from? Do you have a filter or attenuator between the PIC and the
amplifier? (you very probably want a low pass filter).

If the output of the PIC is connected directly to the LM386 then you
should be driving the LM386 hard into clipping with a gain of 200 (in
fact you should be driving it hard into clipping with a gain of 20).

A simple class B (push-pull) output stage with capacitive coupling to
the speaker should do what you want, but it won't deliver any more power
than the LM386, since you are ultimately limited by speaker impedance
and supply voltage.
http://www.ecircuitcenter.com/Circuits/pushpull/pushpull.htm

Regards

Mike

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