[sdiy] Korg MS-50 VCA and VCF

[Harry Bissell]

iirc the base-collector junction fundctions as an excellent very low leakage
diode, with a rather poor breakdown voltage rating.  I've used them that way
in some S/H apps. There are low leakage diodes that have much better voltage
ratings.

H^) harry


----- Original Message -----
From: Colin f <colin at colinfraser.com>
To: 'synth diy' <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 30 Apr 2010 10:07:57 -0400 (EDT)
Subject: Re: [sdiy] Korg MS-50 VCA and VCF

 

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
> Harry Bissell
> Sent: 30 April 2010 14:58
> To: JH.
> Cc: synth diy
> Subject: Re: [sdiy] Korg MS-50 VCA and VCF
> 
> The CA3019 was readily available at that time and had 
> excellent matching due to monolythic construction. It was 
> used in many 'ring modulator' type circuits at the time. A 
> natural extension would be to use it as Korg did.
> 
> BTW, you could use the CA3046 transistor array as diodes in a 
> similar fashion. Just watch the substrate...

The Korg 770 used a TA78 - an array of 5 NPN transistors with commoned
emitters in a SIP package.
Anyone know what pinout is used in the 770 ?
With a common emitter for all transistors, they must be using some of the
base-collector junctions.
Does that make any difference when using a transistor as a diode ?

Cheers,
Colin f



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-- 
Harry Bissell & Nora Abdullah 4eva