[sdiy] switching audio with mosfets

[ASSI]

On Mittwoch, 2. Mai 2007 13:25, Heiko van der Linden wrote:
> I am currently trying to work out a method to switch an audio signal
> with a mosfet transistor.
[...]

What's wrong with using transfer gates?  You'd need one of the analog 
MUX or switch IC that can take around 24V supply (+-12V) or more (like 
the DG4xx).  If you must use a transistor, antiserial connection (with 
the body diodes "inside") of two transistors solves that problem at the 
expense of a considerable loss in performance.  A switch made of only 
n-type or p-type transistors has bad Ron linearity for a wide swing 
signal unless you adopt a constant overdrive architecture (which is 
much more expensive than a switch IC).  The high signal swing can 
easily cause problems with CV feedthrough, so adopting a current-mode 
circuit architecture (VI conversion followed by a switching network and 
possible IV conversion) is probably an overall better idea.


Achim.
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