spikes (was:AW: FETs on the ASM-1 VCO.)

[Haible Juergen]

With all this talk about MOSFETs, JFETs and even diodes:

Is there anything wrong doing it with BJTs ?
I've used bipolar transistors for discharging in my VCOs all 
the time. I haven't done much research myself, just copied what
I saw in many commercial circuits. It works ok, though the spike
in the (converted) triangle could be smaller ...
Is this a general problem with BJTs, I mean do I get much shorter
reset times with FETs ?

IMO, the only reason for ultra short reset time is triangle
conversion. And the problem is worst in LFO applications.
Sure, I know, first rule in Building VCOs: Start with triangle,
not with saw. But then I absolutely love the variable shape
of Osc 3 of the VCS3 for modulation - it's a very unique
effect - and you can only get that when your oscillator core 
is producing a saw wave. So here is an application where
short discharge times are important. (I don't speak of
nanoseconds here, but not of 1nF capacitors either. It's
a 1u electrolytic, if memory serves.) I could improove things
a little when I used a darlington.

JH.