CA3046 subtle design info

[jhaible]

Well yes, that's in the data sheet.
I always connect pin 13 to the most negative voltage which the *array*
(not the whole circuit, mind you) can see. Most negative does not mean
"more negative", i.e. connecting all 5 emitters (including pin 13) to one
node is perfectly ok, for instance. (Did this for my quad expo current
source
in the SSM2040 style filter.)
I've seen circuits from ARP that were even more daring, but you better know
*exactly* what you're doing when you cross that border. (Which ARP surely
did.)

As for -15V (in a +/-15V powered circuit, I asume): Does the array stand
these voltages ? The CB junctions don't. What about the substrate diode ?
(It's in the data sheet, too, but I don't have it in front of me.)

JH.

----- Original Message -----
From: Tim Ressel <Tim_R1 at verifone.com>
To: <synth-diy at mailhost.bpa.nl>
Sent: Thursday, July 01, 1999 7:00 PM
Subject: CA3046 subtle design info


> 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
>
>
>