[sdiy] Adapting exponential convertor for single supply

[Tom Wiltshire]

Thank you all. Phillip, Sam, Roman, Paul, Olivier, Paula, everyone.

This thread is throwing up all kinds of interesting and useful ideas. Too many to use all of them right now, but lots for mentally filing for the next time!

Regards,
Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 27 Jul 2017, at 17:04, Phillip Gallo <philgallo at gmail.com> wrote:
> 
> I have recently tried the Hackaday variant of the 'Perlman' type expo converter. It wasn't the focus of what i was trying, but it met its requirement.
> I used it for a single supply VCO.  
> 
> Earlier this summer, the SDIY list had a thread about a 250kHz to 3MHz VCClock.
> The thread provoked a quick bench-top project to produce an alternative to CD/HC/HCT4046 solutions.
> 
> IThis project gave me the chance to try:
> 1) Rene' Schmitz - type linear CMOS osc
> 2) Hackaday converter
> ... and due to the above, allowed for a single supply +5Vdc VCClock.
> 
> I built this:
> 
> http://www.sdiy.org/philgallo/hfvco/cmosvco.jpg
> 
> My rough eval was of the VCO itself not the expo specifically. VCO Frequency ('scope observations) seemed to demonstrate expo conformity for voltages above the diode derived 'Ref' level and below the High Freq (integrator/reset) droop.  Below 1Vdc it veers off but still allows for very usable selectivity .  
> 
> I didn't trim the VC scaling as the converter was part of a "utility" osc and later changed to a more aggressive scale as i wanted a wide range control response
> 
> I have only built one of these circuits so YMMV but It proved to be a good solution for a HF utility clock for BBD, TOGs, and DigiDelay as it is wide range (meeting original thread requirement) , stable and so easy to build.
> 
> p
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