tri 2 saw modulation II

[Martin Czech]

Another realization:
No frequency error will occour in the following circuit:
Feed the 50% square of a vco into a voltage controlled
integrator. I.e. ota, cap and decoupling op-amp.
The control current of the ota is exponentially controlled
by the pitch c.v. and the symmetry control circuit exactly
the same way as i decribed in my first mail.
This means another expo converter, maybe a cheap one is enough.
So far the circuit is free running, errors could push it to 
the power rails. In order to avoid such offset, the cap is 
reset via electronic switch to the lowest level at the rising
edge of the incomming square. 
This circuit is a kind of hard synced slave osc., no frequency
deviation is possible, but of course this has to be paid for
with amplitude/ waveform error, but maybe this is not so 
important.
Indeed, two vcos could be synced that way, and together with 
the picewise linear network and some additional circuitry
in an additional module this would be a 3 module solution.

It has the same shortcommings than other solutions :
limited ota/expo current etc. but the frequency will be rock-stable.


m.c.