[sdiy] VCS3 oscillators

[harrybissell]

Thank you Ian...

I will consult the "everything" package then.   :^P

I do these spice models by following the published schematics. Its crude but
was effective for the CA3080...which works very well in simulation.

I want to do the 3280 as well.  I have the diode linearization working to some
extent
as it should, but I don't know about the rest

H^) harry

Ian Fritz wrote:

> At 10:46 PM 10/3/2004, harrybissell wrote:
> >The schematic of the 3080 shows Darlington transistors for the PNP
> >mirrors... a sure sign that the PNP gain is low (ie lateral PNP structure)
> >
> >Who knows for the 3280... which does not show the details of the mirrors.
> >Anyone have that info ???
>
> Yesssss ... You need to refer to the Serge T. article in EN #113.
>
> >I'm plating with a spice model (potential) for the 3280... assuming that it
> >is
> >similar to the 3080 in mirror construction.
>
> Nooooo ... Similar, but some fairly significant differences.  Most
> important: the control current mirrors only reflect about 80%.  Thus the
> transconductance equation is roughly
>
> gm = 16 Iabc, compared to
>
> gm = 19.2 Iabc, for the 3080.
>
> Also, if you are using the linearizing diode, twice the diode current is
> mirrored (compared to 1x for the 13600/13700).  And that is actually
> reduced to about 90% of the nominal.
>
> Finally, the biasing scheme of the mirrors makes it impossible to use the
> W. Jung trick of driving the control current through the PS pin.  This will
> actually be the feature I will miss the most (although I bought 100 3080's
> recently).
>
>    Ian