High speed ASM-1 VCO question

[John Speth]

At 11:02 AM 5/2/97 -0700, you wrote:
>   Date: Thu, 01 May 1997 14:52:49 -0700
>   From: John Speth <johns at oei.com>
>
>   I am experimenting with the ASM-1 VCO trying to get it run cleanly at
about
>   100KHz.  I was wondering if you anybody could shed some light on some of
>   design choices that were made in the circuit.  I understand how it works
>   but need info on the more practical aspects.
>
>   My goal is to make a CVable duty cycle modulator for a time-multiplexed
>   panner using analog switches.  I figure I would use the ASM-1 core
sawtooth
>   generator (a standard Electronotes VCO isn't it?) to provide a ramp and an
>   LM311 to make a CVable duty cycle convertor.  Problems I have seen is
>   excessive ringing (about 10% of signal) in the sawtooth at the end of
>   retrace and an LM311 problem (see below).
>
>Umm, I'm confused.  Are you saying that you're planning on using an
>especially-optimized-for-accurate-tracking VCO for a fixed frequency
>source?  Why are you using a sawtooth wave for PWM instead of the
>usual triangle wave?  What are the goals of the circuit? 

I am experimenting with a fixed frequency sawtooth oscillator.  I chose the
EN osc from the ASM-1 because the "technology" was readily available to me,
it was simple, and I was confident I could get a good clean and straight
0-5V saw around 100KHz.  Maybe that's not the case but I'm not ready to
give up yet.

The goal of the whole circuit (saw osc and extra comparator) is to make a
CVable duty cycle convertor.  In other words, a device where 0v means 0%
duty cycle pulse wave at 100KHz and 5v means 100% duty cycle pulse wave at
100KHz.  A saw or tri will work just fine, it doesn't matter.

Does anybody know of a good and simple high freq (100KHz) tri (or saw?) osc
circuit (and where I can find them)?  Certainly a tri wave would mean
ringing would be much less of a problem (no fast edges except for the peaks).

John Speth (johns at oei.com)
Object Engineering, Inc.
Vancouver, WA