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Subject: Re: log-antilog multiplier

Date: 01/08/03 at 6:46 AM
Posted by: David Ashby
E-mail: dashby@quin.contraspam.yuk
Message Posted:

In Reply to: Re: log-antilog multiplier posted by xwindy on 01/06/03 at 6:09 PM:

Hi xwindy,

There's some discussion on lock-in amplifiers in 'Art of Electronics', Horowitz and Hill.

If I recall correctly, one of the waveforms used in the multiplier is just a squarewave, so the other waveform is alternately multiplied by +1 and -1. This can be done by a Gilbert cell, or by using an analog switch (e.g. 4066 or similar). With the analog switch, the signal waveform is alternately passed through non-inverted (effectively multiplied by +1) and inverted (effectively multiplied by -1); the switch is controlled by the reference signal.

Hopefully, this will give you some clues.

David Ashby


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