Saw Frequency doubler and Phase Shifter

[Harry Bissell]

I think in real life... you do NOT want the comparator to go rail to rail
at all... you want it to slew between tightly clamped limits. If you have
less far to go, you get there much faster. The clamps can establish a reference
that is more stable than the rails anyway.  Then playing with the  resistor
values can get you back to the same spot.

These schemes all rely on PERCISE amplitudes for the sawtooth, if you
are off the mistakes will show up as fundamental bleedthrough.

It would also be possible to make a triangle wave first, then make the saw from
that... there are some very clever glitch reduction schemes (Rene Schmitz comes
to mind....).   If the amplitude of the triangle is off, it won't affect anything
as long
as there is no DC offset  (easier to guarantee I think than the amplitude...)

Then you can use an invert/non-invert switch to make the sawtooth.  The long way
around I admit but might be easier ???

H^) harry

Magnus Danielson wrote:

> From: jorgen.bergfors at idg.se
> Subject: Re: Saw Frequency doubler and Phase Shifter
> Date: Mon, 18 Sep 2000 8:56:22 +0200
>
> > Hi Magnus and everybody else.
>
> Hi Jörgen and everybody else who cares to read this...
>
> > You really need a faster comparator than a TL082 for this to work
> > satisfactorily. I used an LM318, and that was for LFO frequencies.
> > For audio frequencies something even faster would be desirable. At least if
> > you intend to do any further waveshaping on the output.
>
> Jörgen is offcourse correct. My schematics is to display the general idea and
> principle and does not convey all the practical details like slewrate etc.
> which haunts a real design. The choice of TL082 is just as arbitrary as picking
> an uA741, NE5532 or LF411. No real thougth has gone into that part of the
> design.
>
> The comparator part is really critical since it shall go basically rail-to-rail
> in both directions quickly.
>
> Cheers,
> Magnus