Oscillator idea come's unstuck

[Fraser, Colin J]

> -----Original Message-----
> From: Rene Schmitz [mailto:uzs159 at uni-bonn.de]
> Sent: 17 January 1999 23:05
> To: Fraser, Colin J
> Cc: synth-diy at mailhost.bpa.nl
> Subject: Re: Oscillator idea come's unstuck
> 
> I don't want to discourage anyone, but either its that the 
> two switches are
> conducting simultaneously. (as Jürgen said)
> But I suspect another thing: I've read in Horowitz & Hill Chapter 3.12
> "Limitations of FET switches", that some (and they mention 
> the 4066) analog
> switches have the nasty property to short (!) the input to ground
> momentarily. 
> If that might happen, then the charge would leak to ground.
> I would try it with a 4016 which is different to 4066.

This could be it - I tried various different 4066s to see if I got different
results. With one device there was a noticable spike at the top of the
triangle wave - but the wave continued normally after this. This spike could
be the result of the momentary short mentioned.

> Apart from this it might could be that the R(on) of the 
> switch varies with
> the voltage on its inputs. The 4066 is better in this regard 
> than the 4016. 

IIRC the 4016 has the same pinout as the 4066, so I'll get hold of one and
try it in the circuit.
Maybe the best bet is to use discrete FETs.


Colin f