[sdiy] VCO reset time

[Czech Martin]

or a mosfet. Has it been tryed to use the cap in a miller fashion?
The it would be almost virtual ground.

m.c.

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of JH.
> Sent: Mittwoch, 2. Juni 2004 23:14
> To: music.maker at gte.net; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] VCO reset time
> 
> 
> > Yes, the René Schmitz 4069UB VCO is an example of a core 
> that uses no
> > opamps at all.  Do you think the ALD1103 series you've previously
> > mentioned might be better?  That's quite a good VCO for 
> such lowly and
> > inexpensive beginnings as a 4069UB.  Did you have other 
> structures in
> > mind besides the dual complementary MOSFET inverter?  I was 
> thinking that
> > generally the MOSFET technique would be good due to low leakage.
> >
> > I suspect that the ALD part might be quite superior because it's on
> > resistance (for cap discharge) is typ. 180 ohms compared to 
> approx 5000
> > ohms for the 4069UB (calculated from data sheet approx 3 ma 
> source drain
> > current at 15 volts at around room temperature).  Or is 
> this way off?
> 
> 
> A simple FET source follower will do. No need to build an 
> active integrator.
> Drawback: expo converter will not work into a virtual GND 
> node anymore.
> (Does this matter?)
> 
> JH.
> 
>