[sdiy] low rbe tranies?

[Ian Fritz]

At 03:35 PM 9/14/2003, Jay Schwichtenberg wrote:
>Does anyone know of some discrete transistors with low rbe that can be
>matched for expo converters? Other than the temp issues this seems like a
>good criteria for selecting expo transistors.
>
>Thanks
>Jay

Jay --

Low Re definitely helps with hf tracking issues, provided you have a good 
clean waveform.  (Hi beta is also nice.)

For npn use the CA3083 array.  Re =1.27 Ohm, better than the 5.0 Ohm of the 
CA3046.  Optionally, the LM394 has Re = 1.1 Ohm.  Of course MAT02 is even 
better, if you want to pay for it.  No need to, in my experience.

For pnp try the Zetex ZTX794A (available fro Digikey).  Re = 0.12 Ohm, and 
high beta to boot.

   Ian