New idea sawtooth generator (fwd)

Rick Jansen sscprick at
Tue Jul 11 09:52:39 CEST 1995

In message <Pine.3.89.9507101851.B21023-0100000 at> you write

> Uh oh.  Now you've caught me.  :)  I can't see what the problem is
> with the old sawtooth generators, that a new one is needed ....

There's the reset time, the time needed to discvharge the integrator
capacitor. In many circuits a period of ca 1 microsecond is used to
fully discharge the cap, which is 1% of the wave period at 10kHz.
You can compensate for this at the cost of sawtooth amplitude, by 
starting the discharge cycle a bit earlier at higher frequencies.

> 4066 switches?  I don't know the specs of them off hand, but these are
> high voltage switches.  Why not use 4016 switches?  (The latter I know
> of a 300 ohm ON impedance).
> Or how about JFET transistors as the switches?

The 4066 and specifically the HC4066 have better specs than the 4016
and general JFETs. The R(on) of the HC4066 is 25 ohm. R(on) of JFETs
is from 30 ohm to a few hundred ohm. I prefer the (HC)4066 as it seems
an ok switch and it is readily available.

Rick Jansen
rick at
S&H's a module and s&h's looking good

More information about the Synth-diy mailing list