[sdiy] More about the Aries VCO

[James Patchell]

I myself have also used the LM311 as a comparator in both saw (ASM-1 type) 
and triangle VCO's with excellent results.  Don't know why, but in 
breadboards, I always manage to wire the power supply pins up 
wrong....(somehow, I always got them correct on PC boards....)....

At 11:56 PM 6/14/2004 +0000, harrybissell wrote:
>The 3080 has a slew of like 80V/us which puts it above opamp class (as
>comparator)
>but below the std LM311 etc. It is a very well behaved comparator and i 
>have used
>it
>often as such...
>
>H^) harry
>
>Ian Fritz wrote:
>
> > At 04:04 PM 6/14/2004, JH. wrote:
> > >Now that I know the internals of the expo onverter, I've taken a 
> closer look
> > >at
> > >the whole thing.
> > >
> > >This CA3080 based schmitt trigger is very clever! Must be pretty fast 
> *and*
> > >precisely bouding at fixed level without saturating.
> > >(Does anybody know at what current it is working, i.e. the value of the
> > >resistor at pin 5 of U4 ?)
> > >
> > >I still wonder if it is *that* fast (and if the transitors have such low
> > >rbb) such that
> > >it doesn't need any HF tracking compensation ?!
> >
> > I haven't looked at the Aries, but the 3080 as Schmitt trigger was used by
> > Bernie in the ENS-76 series.  See EN#75, p. 10, or the builder's
> > guide.  The integrator is a 3080 driving a 1 nF cap buffered by a 3140. The
> > Schmitt trigger output is diode clamped.   There is no hf
> > compensation.  The tuning wasn't measured to high precision, but it looks
> > like it goes sharp (!) by 0.5% at the high end (24 kHz).
> >
> >     Ian

         -Jim
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