[sdiy] How To Make This Oscillator into a VCO

[Scott Gravenhorst]

One way is to replace the integrator opamp with an OTA (and some
other changes, like referencing C1 to ground instead of the 
integrator input).  The LM13600 data sheet has an example of
such a circuit.

What you need is to replace R1 with a voltage variable current 
source, but in this application, that's not so easy because the 
schmitt trigger output keeps switching from one rail to the other, 
reversing the polarity of the charging current each half cycle of
the oscillators output.

A vactrol as R1 would work, but I'm not sure how linear that would be.

bill berzinskas <housenationmedia at yahoo.com> wrote:
>--0-788137908-1035048867=:7746
>Content-Type: text/plain; charset=us-ascii
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>
>Hey everyone.. 
>
>A week or so ago, I put out my schematic for an oscillator I was 
>working on.. I got some good responses, and I've designed this 2 
>opamp oscillator (schmitt trigger and integrator).. My question 
>now, is how would i go about making this into a vco? you can see 
>the schematic here: http://hnrserver.dynip.com/oscschem.jpg Any 
>help is appreciated! --billie --------------------------------- 
>Do you Yahoo!? Y! Web Hosting - Let the expert host your web site 
>--0-788137908-1035048867=:7746 Content-Type: text/html; 
>charset=us-ascii <P>Hey everyone.. </p> <P>A week or so ago, I 
>put out my schematic for an oscillator I was working on..  I 
>got some good responses, and I've designed this 2 opamp 
>oscillator (schmitt trigger and integrator)..  My question 
>now, is how would i go about making this into a vco? </p> <P>you 
>can see the schematic here:  <A 
>href="http://hnrserver.dynip.com/oscschem.jpg">http://hnrserver.dynip.com/oscschem.jpg</a></p> 
><P>Any help is appreciated! </p> <P>--billie</p><p><br><hr 
>size=1>Do you Yahoo!?<br> <a href="http://webhosting.yahoo.com/ 
>">Y! Web Hosting</a> - Let the expert host your web site 

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