[sdiy] More VCO fun

[Ian Fritz]

At 12:34 AM 12/8/2009, David G. Dixon wrote:
>...and the winner is...
>
>Oren Leavitt!!!  (and the crowd goes wild as the camera pans to a tearful
>synth-diyer standing on the podium with hand on heart underneath an enormous
>flag as the anthem is played in cheesy Casiotone monophony...)
>
>I just simulated your solution, and it is WAY BETTER!  Resetting is
>occurring in just about exactly one microsecond.  My feeble, inappropriate
>JFET is now truly happy!  And, the kludge will be incredibly easy on my
>existing layout, which is a bonus.

Yes, one sees Oren's method commonly used in S/H circuitry also.  In 
Terry's design the comparator is pulled up to 0 V, which is all that is 
needed because of the large pinchoff voltage of the JFET.  This limits the 
total swing of the comparator to 15V rather than 30 V, somewhat reducing 
problems with transients.  Pretty clever and effective, it seems to me!

Ian