[sdiy] filtering out a saw-reset glitch in a triangle shaper

[David G. Dixon]

Incidentally, I also tried an active clamp (opamp + diode) based on the 5V
reference voltage instead of the zener, but the slew rate limitation of
TL074 in active clamp mode was enough to allow the glitch through.

In fact, even without the zener, the glitch is reduced to practically
nothing just by the strategically placed pF-range caps.


> > I'm actually liking the active full-wave rectifier plus 5.1V zener
> > method
> > more and more.  Slap a 15pF cap across the feedback loop of the
> > final level
> > shifting and inverting opamp, and the final -5 to +5V triangle looks
> > virtually perfect.
> 
> Haven't followed the thread too closely, so I don't know the details
> of this circuit; but did you take the tolerance of the zener voltage
> into account? Looking at the data sheet of a random 5.1 volts zener
> diode (1N5231B), the voltage can vary between 4.845 and 5.355 volts.
> So if you're unlucky, either a bit of the glitch will still be there,
> or your triangle gets quite mis-shaped. Or you need to trim the
> amplitude or offset of the triangle.