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In the synthesizer world there is a standard called "1V/octave" which basically refers to a linear input voltage corresponding to a logarithmic change in frequency (e.g. 1V = 100Hz, 2V = 200Hz, 3V = 400Hz, 4V = 800Hz and so on).

All the schematics that I can find are made for symmetric power supply and they only work with positive voltages. Now when I convert those schematics to my single supply environment I can only use voltages between 4.5V and 9.0V (I run on a +9VDC power supply). I have spent days modifying these circuits to my need but I don't have any luck.

Here's one of the many circuits provided by the internet:

enter image description here

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  • \$\begingroup\$ Do you still need 1V/octave response? How many octaves do you want to cover? \$\endgroup\$ – Chris Johnson Feb 14 '14 at 17:47
  • \$\begingroup\$ What did you come up with? \$\endgroup\$ – Matt Young Feb 14 '14 at 17:50
  • \$\begingroup\$ So you actually want a circuit with exponential response? \$\endgroup\$ – Spehro Pefhany Feb 14 '14 at 18:47
  • \$\begingroup\$ Hello guys, sorry for the late response, I was sick... Yes, 1V/octave and well, as many octaves as I can get...? I guess something like 5 would do the trick. And I believe, yes, it is a exp response that I want. Thanks for you help guys. \$\endgroup\$ – user35474 Feb 18 '14 at 13:43
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Try using one of these: -

enter image description here

I've also been down this path before and the only recommendation I can give (because I haven't found a log VCO that can run on lower supplies) is to increase the supply. At least with this device it'll run from supplies as low as 4.5V and all the way up to 18V.

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