[sdiy] VCO waveform logic selection

Mattias Rickardsson mr at analogue.org
Tue Sep 11 16:20:15 CEST 2007


How about doing the Prophet~5 trick and putting the 4051 on the other
side of the resistor, namely at an OPamp input where it's at virtual
ground potential? This will let it eat any signal level, and will also
prevent distortions caused by the 4051 on-resistance varying with
input voltage.

If I've understood things correctly. :-)

/mr


On 11/09/2007, Michael Ruberto <frankentron at hotmail.com> wrote:
> JB
>
> You could try a better device for starters. Get samples of the ADG333 from
> Analog Devices. They handle signal levels up to the supply rails and have
> 2.4V HI level digital inputs.
> http://www.analog.com/en/prod/0%2C2877%2CADG333A%2C00.html
>
> M. A. Ruberto
>
>
> >From: jbv <jbv.silences at club-internet.fr>
> >To: synth-diy at dropmix.xs4all.nl
> >Subject: [sdiy] VCO waveform logic selection
> >Date: Tue, 11 Sep 2007 11:12:53 +0200
> >
> >Hi guys,
> >
> >Let's say I have a vco module that outputs various waveforms at +-5V.
> >And I want to digitally select 1 of these ouputs to send it to the input
> >
> >of another module. What is the best way to proceed ?
> >
> >would some analog mux like the 4051 do, if its power supply is set
> >to +-7.5V ? If yes, how to handle logic selection signals, especially
> >if they're generated by 3V logic uC ?
> >
> >Thanks in advance,
> >JB
> >
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