[sdiy] Futurlec has LM394's for cheap

[René Schmitz]

Hi Harry and all,

Harry Bissell Jr wrote:
> How is the LM394 at that. I did not see a spec for it
> (or at least a direct spec)

I used them (metal can version) in the first two Oakley TB3030's I 
built, but never have measured their expo conformance. (I should be 
getting them out of there to run some tests.)

The LM394 is the original super matched pair, and plays in the same 
league as MAT02, the SSMs or the like.
The key difference to "cheap" (thats now relative) pair transistors is 
the interdigitation of the transistors (common centroid layout). Also 
it is a large geometry device which you can think of as lots of small 
transistors in parallel, so the noise goes down, and temperature 
gradients across the chip have little consequence.
*That* is why its superior to the more humble 1583, 3083, 3086 and the like.

Whether the Rbe is now lower or higher by 0.1ohms compared to the other 
pairs really is pointless. (Besides I measured lower Rbe on a BC548C 
(costs 0.07€) than on a MAT04... Now is that the better transistor?)

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159