[sdiy] Compensation for triangle amplitude getting bigger at higher frequencies?

René Schmitz synth at schmitzbits.de
Tue Aug 29 17:03:14 CEST 2023


Why doctor on the symptoms? Use something faster for the schmitt 
trigger. LM311/393, CMOS Gates, 7555 etc...


Best,

  René


Am 29.08.2023 um 16:27 schrieb Neil Johnson via Synth-diy:
> Maybe try a little Franco comp in the integrator?
>
> Neil
>
> On Tue, 29 Aug 2023 at 14:42, Scott Bernardi via Synth-diy
> <synth-diy at synth-diy.org> wrote:
>> I've breadboarded a VCO with an OTA (as switch) - Integrator - Schmitt trigger triangle / square wave generator at its core. I've noticed that at higher frequencies, the amplitude of the triangle wave gets larger. Like the output of the schmitt trigger is delayed in switching.  I'm using parts of a TL074 in the integrator and schmitt trigger.
>> Is this because the rise and fall times of the TL074 become a more appreciable part of the waveform time?  TL074 has 13 V/uSec slew rate, which traverses the ~22v in about 1.7uSec, or the +/-5v trigger points in a bit under 1uSec.  Even at a top frequency of 16kHz, that's about 2% of the total period.
>> Is there a way to compensate for this?
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