>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 09 August 2005 23:53
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Floating Analog Signal in
>
>
>> The peak detector is what I described, without knowing what it was 
>> called.  It is sufficient for what I need.  (This is not precision, 
>> just an indication of relative volume level.)  My problem is before 
>> that.  I need to be able to translate an audio signal that is 
>> referenced to audio ground to a signal with its reference to digital 
>> ground without connecting the grounds together.
>
>Hi Phil,
>
>You're looking for a differential amplifier or instrumentation 
>amplifier.
>
>Are the two grounds tied together somewhere? Because if they 
>are not at the same voltage you will need to do pay attention 
>to that when you design your amp.
>
>Cheerful regards,
>
>Bob


A good, old fashioned transformer would also do the job, but of course the resulting signal will be AC so will need rectifying for the peak detector.

Regards

Mike

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