[sdiy] Discreet Dual Pulse Gen

[Michael Ruberto]

The input may need to be amplified for this scheme to work properly. Once 
the proper level is achieved the only limitation to the pulsewidth should be 
the hysteresis of the Schmitt triggers. One way I can lower the turn off 
time is by running the Schmitt triggers from a lower supply voltage. +/- 5V 
would be ideal with the 2.5V threshold.
With a 10V PP input signal I would have a 5V peak for each trigger after 
half wave rectification. Hmmm yeah a X2 gain will be needed.

Ok what if I ditch the vactrol and use a bipolar CV to DC level-shift the 
input signal?

M. A. Ruberto


>From: Ian Fritz <ijfritz at earthlink.net>
>To: "Michael Ruberto" <frankentron at hotmail.com>, 
>synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] Discreet Dual Pulse Gen
>Date: Sun, 28 May 2006 07:38:26 -0600
>
>Interesting.  Will you have enough gain to get close to the square-wave 
>limit?
>
>   Ian
>
>At 05:10 PM 5/27/06, Michael Ruberto wrote:
>>I have been attempting to simplify the design of the dual pulse generator. 
>>It has been completely redone with mostly discreet circuitry. There may be 
>>some blunders in the design so I appreciate corrections.
>>
>>http://frankentron.freezope.org/source/idea1.gif
>>
>>The heart of the circuit is two Schmitt triggers. They are setup to 
>>trigger at about 2.5V. The idea is that one detects the Negative portion 
>>of the input wave and the other triggers on the positive. A vactrol 
>>controls the amplitude of the input signal which provides a pwm function. 
>>The outputs of the 2 schmitt triggers are level shifted by a varying bias 
>>from pin 7 of the opamp. As this bias increases to positive the pulse from 
>>the positive Schmitt will be reduced in amplitude and the negative pulse 
>>increased in amplitude where the 2 pulses are mixed together. This gives a 
>>means of controlling the symetry of the output pulse with a CV.
>>
>>If anybody is feeling froggy I'd love to know if it will work in a 
>>simulation before I hunker down with a breadboard for a couple hours.
>>
>>M. A. Ruberto
>>
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