[sdiy] Replacing CA3080 with CA3046 ??

[Tim Parkhurst]

 Seems like a discrete transistor OTA might not be the best (or easiest) VCA
solution. Check out Jorgen's VCA comparison at

http://www.idg.se/personal/bergfors/bergfotron/VCA.htm

This comparison shows that actually the lowly 13600 makes a pretty darn good
VCA. This list includes the 3080 , the SSM2024, 3046 and 3086-based OTAs,
amongst others. It doesn't include the 3280 or 5517 however. 


Tim (pretty good by comparison) Servo

*******************************
-----Original Message-----
From: srnovak at ncsu.edu
To: synth-diy at dropmix.xs4all.nl
Sent: 4/8/05 11:14 PM
Subject: Re: [sdiy] Replacing CA3080 with CA3046 ??

Another thought in comparing MAT04 with CA3046 is that each chip was
designed for it's technology (i.e. junction isolation Vs. trench
isolation). The Collector-Emitter breakdown voltage of the MAT04 is 40V,
where the Colector-Substrate breakdown voltage of the CA3046 is 20V min
and typical is 60V. I was planning on running off single 12V, but even
with a dual 12V supply, it seems both chips would be in no danger of
parisitic diodes or BJT's as long as the substrate was at the lowest
voltage (also assuming I have a little better then the worse CA3046).

	From: 	  patchell at cox.net
	Subject: 	Re: [sdiy] Replacing CA3080 with CA3046 ??
	Date: 	April 8, 2005 11:12:09 PM EDT
	To: 	  samppa.tolvanen at gmail.com, madhun2001 at yahoo.com
	Cc: 	  srnovak at ncsu.edu, synth-diy at dropmix.xs4all.nl

The MAT04 is dialectically isolated (the CA3046 is junction
isolated)...also, the THAT 3xx transistor arrays are dialectically
isolated, so you don't have to worry about which pin is more negative
that
which...

However, in general, building your own OTA is sortof a loosing
proposition.  However, I have made simple OTA's, using a THAT340 PNP/NPN
array (two NPN's and two PNP's) that work out pretty good for cloning
the
SSM2040 VCF...still...it is a rather expensive solution...

        -Jim

At 03:13 AM 4/9/2005 +0300, Samppa Tolvanen wrote:
On Apr 9, 2005 1:43 AM, Tim Ressel <madhun2001 at yahoo.com> wrote:
> Yo,
>
> Don't forget the oft overlooked pin 13 requirement.
> The substrate of the IC (pin 13) needs to be at the
> lowest voltage the part is likely to see. Otherwise
> some internal dides conduct and spoil the party. Keep
> this in mind when designing Q5 into your circuit.
>
> --Tim Ressel (rubbing the scar where he was bit...)
>
?
Could MAT-04's have some "bias". pleaseee? LIke a negative one-- down
there.. anx, Samppa
害. Down  I went

        -Jim
***************************************************************
http://www.oldcrows.net/~patchell

***************************************************************






***************************************************************************
This message is confidential.  The information contained in
this e-mail message is intended only for confidential use of the
recipient(s) named above. If the reader of this message is not the intended
recipient or an agent responsible for delivering it to the intended
recipient, you are hereby notified that you have received this document in
error and that any review, dissemination, distribution, or copying of this
message is strictly prohibited.  If you have received this communication in
error, please notify us immediately by e-mail, and delete the original
message.
***************************************************************************