> -----Original Message-----
> From: David VanHorn [SMTP:dvanhorn@CEDAR.NET]
> Sent: Sunday, February 10, 2002 8:49 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [pic]: Can you amplify with a single 2n2222 ??
>
> At 01:59 PM 2/10/02 -0800, rad0 wrote:
> >let me give this a try - thanks
>
>
> If you have a pair of output pins, you can do a bridge drive, but be
> careful.
> You want to take both pins to the same state, before taking them to
> opposite states.
>
> 00,01,11,10,00... rather than 10,01,10...
>
> The reason is that with the second sequence, you make a capacitive voltage
> doubler, and are sinking large current pulses into the protection diodes,
> risking CMOS latchup.
>
You could do the push-pull using the proposed 2N2222 transistor.  Configure
the transistor on common emitter mode as sugested with a 1k collector load.
Then connect PIC pic to the transistor base via a 10k resistor and also to
one side of the piezo.  The other side of the piezo goes to the transistor
collector.

Mike

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