[sdiy] Tri to Saw converter produces a weird waveform

[Scott Bernardi]

Yep, that was it. I had to go back to an npn transistor with a series diode
and resistor driving the base (I was hoping the MOSFET would give me a
sharper edge on the top of the sawtooth. It's a bit rounded with the npn).

On Sat, Dec 13, 2025 at 12:41 PM Donald Tillman <don at till.com> wrote:

> On Dec 13, 2025, at 12:06 PM, Scott Bernardi via Synth-diy <
> synth-diy at synth-diy.org> wrote:
>
>
> I built a tri core vco and used a typical method to convert the triangle
> to a saw using the invert - noninvert of the triangle and adding the square
> back in.  Schematic and the waveforms I get are on this page:
> Weird Saw <https://www.bernacomp.com/elec/og2/weird-saw.html>
>
> Any ideas what's going on and how to correct it?
>
>
> The 2N7000 has a parasitic diode between the drain and the source, so it
> will start conducting if the drain goes more than 0.6V negative.
>
>   -- Don
> --
> Donald Tillman, Palo Alto, California
> https://till.com
>
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