[sdiy] More about the Aries VCO

[harrybissell]

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