[sdiy] uA726 transistor array

[Ian Fritz]

At 10:25 AM 10/14/2002, Jay Schwichtenberg wrote:

>I did say that it was for an expo converter.


Yes, but you have two choices for a temperature-stabilized expo 
converter.  (1) You can use the usual differential-pair type.  (2)  You can 
just use the exponential response of a single transistor.  I was saying he 
may have been thinking of (2) rather than (1).


>If I remember correctly it was something to do about noise.

Noise is an issue, and it is usually not brought up when the heated expo 
topic comes up here.  I noticed a long time ago that the SSM 2033 VCO has 
some noise from the heater servo circuit.  You can hear it by tuning the 
frequency above the audible limit and cranking up the gain of your 
monitoring system.  The noise goes away when the heater is 
disconnected.  It's not a lot of noise, but it is there.  It's still not 
clear why this would be worse with the That arrays, but again possibly 
something to do with the dielectric isolation as Jim brought up.

   Ian