matched transistors

[Ian Fritz]

I would propose some softening of this statement. If you just go by the spec
sheets, then yes, the inexpensive arrays seem pretty bad. However, as I have
mentioned previously, modern parts often far exceed specs. For example I
recently bought a half dozen CA 3083's. All but one have offset voltages too
small to measure reproducibly -- < 0.2 mV. Betas are well over 200. Series
resistance is only 1.3 Ohm (which can be exactly compensated with a diode
and a trimpot, anyway). Are you sure you need a lot better than this? Have
you compared the other sources of error and drift with those stemming from
using this "cheap" array?  I'm using one of these in the VCO I'm currently
developing, and I don't see much (if any) difference in performance going to
an expensive pair.

  Ian

----- Original Message -----
From: "Haible Juergen" <Juergen.Haible at nbgm.siemens.de>
>
> Depends on the application.
> When you're talking about CA3046 and the like, these are fine if you only
> need
> equal temperature for both transistors. In some applications you also need
> low offset voltage, low offset voltage drift, high beta, low noise. Then
the
> cheap
> array will not do.