CA3046 subtle design info

[Tim Ressel]

To all--
This bit me as I wired in a 3046 as a heater element in my VCO design:

Quote from the 3046 data sheet:
"The collector of each transistor of the CA3045 and CA3046 is isolated from the
substrate by an integral diode. The substrate (Terminal 13) must be connected to
the most negative point in the external circuit to maintain isolation between
transistors and to provide for normal transistor action."

It turns out that these intrinsic diodes can wreck havoc as the partially
conduct or leak or whatever they do.
My solution was to not use the pin 13 transistor and just tie pin 13 to -15V. I
hope this info helps anyone who 
is seeing weird stuff in their circuits.



Tim Ressel -- Hardware DQ
Hewlett-Packard
Verifone Division
916-630-2541
tim_r1 at verifone.com