[sdiy] variable width pulse wave for JEFT sample and hold

[Dan Snazelle]

ok...so it sounds like a n channel fet gets triggered by a NEGATIVE pulse.

i will check everyones great ideas

thanks!!






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> Date: Tue, 6 Jan 2009 11:49:05 -0700
> To: dixon at interchange.ubc.ca; subjectivity at hotmail.com; synth-diy at dropmix.xs4all.nl
> From: ijfritz at comcast.net
> Subject: RE: [sdiy] variable width pulse wave for JEFT sample and hold
>
> Or use Bernie's S/H technique. Fire a 555 timer powered between 0V and -15V.
>
>
> At 11:19 AM 1/6/2009, David G. Dixon wrote:
>
>>Why not just use an RC high-pass filter with a time constant of about 10 us
>>to generate spikes from the square (0.001 uF and 10 k will do nicely), and
>>then shift the pulses with a unity-gain inverting opamp with a voltage 2:1
>>divider off the positive input between -15V and 0V so that the output DC
>>rides at about -5V and the spikes go up to 0V to trigger the JFET (which, I
>>presume, is npn and therefore is full off at about -3.5V and full on at
>>about 0V)?
>