[sdiy] VC Switch schematic?

[harry]

Uhh yeah... I'm with Scott on the DG series switches (Maxim, Siliconix).

There is another trick to use... you can use the CMOS 4016, 4066, 4051..2...3
etc..
if you bias the negative supply pin to -0.7V (one diode drop below ground) and
locate the switch at the summing junction of an inverting opamp (the inverting
input).

This way, very little voltage is developed across the chip... and it can still
run off the
normal 12 to 15 volt supply.

Sequential Circuits Prophet V did the switching like this... cheap and clever.

But the DG is a safer bet and pretty cheap these days as well...

H^) harry

Scott Bernardi wrote:

> Probably the easiest way to implement voltage controlled switches is with
> analog switches like the DG201 series. These have 4 SPST switches per
> package that can be controlled by a logic signal for on/off.  They can
> handle full range analog signals (i.e., +/-15v).  They are a bit pricey,
> though.
> They next alternative would be to use the cheap 4066 CMOS switches.  These
> can take a maximum of 16v across the chip, though, so you would have to
> make some +/-7.5v supplies to power them, and then the logic levels are
> -7.5v (off) and +7.5v (on).  They can handle analog signals up the the
> supply values (+/- 7.5v), which is a problem if you need to handle 10v
> peak signals.
>
> If you want to implement a "select one of many" function you can use a
> demultiplexor.  There are analog ones and CMOS ones available with the
> same restrictions as above. Juergen Haible has an interesting circuit, the
> "Interpolating Scanner" which does a demultiplex function with a smooth
> transition from one input to the next (crossfade) under voltage control.
> http://home.t-online.de/home/jhaible/jh_ipscan.html
>
> ElmacacoX at aol.com wrote:
>
> > Hey everybody,
> >
> > Does anybody have a VC switch schematic on their website or something?
> > I'm looking to add one or two to my SBM.
> >
> > thanks,
> >
> > Ed
>
> --
> Scott Bernardi
> sbernardi at home.net

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