[sdiy] super simple portamento / slide / glide / slew limitingcircuit?

[David G Dixon]

> http://www.elby-designs.com/asm-2/glide/glide-asm2-about.htm
> 
> Switchable lin and log response. One dual op amp, two 
> resistors, cap, pot, switch.

I don't like that circuit at all!  The comparator will oscillate in linear
mode, generating about a 10V p-p sine wave at about 7400 Hz or so which
takes a very long time to dampen out.  This will create high-frequency
warble of several mV in the output.  I believe this circuit requires a large
resistor in the negative feedback loop of the comparator -- 100k gives a
smooth approach to the input voltage with rapid damping (less than half a
millisecond).  Also, the buffer benefits from a capacitive load protection
network.  Finally, the switch could be much simpler -- an SPDT will do if
it's hooked up properly.

Again, email me privately for details.