Anonymous
10/25/2025, 6:13:04 PM
No.2953079
>>2953075
Not really, I did design it with the option to use a thermistor on the feed back for the opamp that drives exponential circuit.
The dialectic material for the NP0 caps have very low leakage leakage which is vital for this circuit because the timing cap is only 220pf and I expected the VCO to work down to 30Hz, with very little distortion. The result of this is that current control on the OTA is down to pA's for minimum frequency. This makes it very sensitive to leakage current, even surface contamination on the board can get it out of tune.
I had to wash the finished board under the tap and then drown it in alcohol to get it stable.
Not really, I did design it with the option to use a thermistor on the feed back for the opamp that drives exponential circuit.
The dialectic material for the NP0 caps have very low leakage leakage which is vital for this circuit because the timing cap is only 220pf and I expected the VCO to work down to 30Hz, with very little distortion. The result of this is that current control on the OTA is down to pA's for minimum frequency. This makes it very sensitive to leakage current, even surface contamination on the board can get it out of tune.
I had to wash the finished board under the tap and then drown it in alcohol to get it stable.