The noise is due to RF demodulated at the amps input.  We have a lot of
experience on this problem regarding cellular phone noise.  Good grounding
and bypass caps at the inputs should solve this.

regards,
Reggie

----- Original Message -----
From: "Hopkins" <rdhopkins@IHUG.CO.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, September 29, 2003 1:06 PM
Subject: Re: [EE:] Hands Free...


> Try bypassing power supply pin near each chip with a 0.1uf cap to ground.
>
> :-) Roy
> ----- Original Message -----
> From: "Eduardo Garcia" <egnascimento@YAHOO.COM.BR>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Monday, September 29, 2003 3:57 AM
> Subject: [EE:] Hands Free...
>
>
> > Hi!
> > I am with a "begginer problem" an hope that all can help me ;-)
> > I am working in a hands free for gsm module but the peaks on power
supply
> > are inducing a noise in voice output.
> > I have inserted a 2200uF/16v cap at power supply out but this peaks
> remain.
> > I know that can't connect Analogic GND with Digital GND, so my
suggestion
> > circuit use lm386 (8R speakers amplifier) and follow attached!
> >
> > 1- PLEASE, HOW CAN I REMOVE AUDIO NOISE FROM OUTPUT?
> > 2- IS THERE ANOTHER (AND BETTER) WAY TO DISCONNECT AGND AND DGND?
> >
> > Thanks all in advance,
> > Eduardo Garcia
> >

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