SergeModular

>> Have you found a good spice model of the LM3900 / MC3401?


> I don't believe there *are* any manufacturers models for the
> 3900/3401 out there.

I suppose an email to National Semiconductors (2900/3900) or
Motorola (3301/3401) might be worth a try. Or try Bob Pease (c:

> Ack. It's unfortunate that the standard SPICE BJT model doesn't
> model such things as reverse junction breakdowns, as it does for
> diodes.

That's why it's called a model I suppose. Same reason that James
May's full size Airfix Spitfire wouldn't fly...

> Camenzind's excellent book for the stuff about parasitic devices,

It's on my reading list, which is longer than my remaining
life expectancy...

>> The other surprising thing is that switching on transistor
>> 6/7/8 doesn't cause excessive current to flow into pin 8
>> of the MC3401 and cause blowupedness


> Presumably the big discharge current merely circulates
> cap-33R-transistor, so the input pin isn't really involved.

Ideally.

>> Have you found the almost-exponential converter yet?


> I'm actually looking at improving the 'controlability' of the
> Plan B M10: it seems the core of that circuit is virtually a
> direct copy of the Serge envelope generator,

The designer / copier (delete as appropriate) is/was a member
of this list. Perhaps he'd like to contribute?

> maybe 15-20 percent of pot travel, and the relationship between
> rise/fall/timebase pots means there are large portions of travel
> which simply have no effect.

The same circuit crops up in several first generation Serges,
including the Neg, Pos and VCO. I tried strapping a decent
current source to the VCO and it was much improved.



Steve