Should I use 1 transistor array for 2 exponential converters

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

Hi!

I want to build a dual 4069 vco (by Rene Schmitz http://www.schmitzbits.de/vco4069.html ) on one little pcb.
I replaced the pwm with a opamp version so I only need 1 cd4049 plus 1 tl074 for 2 VCOs...also the edges of the pulse wave are a bit 'sharper'.
It's working quite well on a breadboard so far...

I thought that it would be convinient to use a ca3096 (3 NPN + 2 PNP) for the two exponential converters.
My question is:
Is it ok two have two exponential converters i one packadge??
And if so, if I want to use a tempco , do I just stick both of them on op of the ca3096?

And also, would it be ok to use the 'leftover' NPN in the ca3096 for something else, or could it disturb the tempco somehow?

JovianPyx · Posted: Sun Aug 31, 2014 3:32 pm Post subject:

I can't help with the array, but I noticed that you cited a part CD4049. I assume that you meant 4069. The circuit was designed for a 4069 and may not work correctly with 4049.

Also, it may not be advisable to put 2 VCOs on one 4069. I realize that there are enough gates, but the close internal power coupling of the two circuits on the same IC may have a problem with soft synch. There can also be a sensitivity to the exact gates that are use for schmitt trigger and integrator.

Hopefully Rene will see this.

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna