[sdiy] Matched Transistor Specs

Mike Beauchamp list at mikebeauchamp.com
Tue Sep 1 20:55:58 CEST 2020

On 8/31/20 6:21 PM, Aaron B. wrote:
> I've been looking at dual transistors for exponential circuits. If I'm
> okay with surface mount, there seems to be a bewilderingly large number
> of parts available.
> Besides the maximum voltage/current ratings, what should someone look
> for in a good exponential converter pair? Do any of the typically
> published specs like Vceo, Is, beta, etc matter much in this use case?

Hi Aaron, I've recently been using DMMT3906W ( 
https://www.diodes.com/assets/Datasheets/ds30312.pdf ) in an exponential 
converter and have been very happy.

Previously I was hand-matching transistors using Bob Moog's published 
schematic but this part has performed noticeably better. I can't speak 
for the specs of this part or if this is the absolute best option, but I 
can tell you that my oscillators are more stable with it.


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