current mirrors (was: AW: [sdiy] discrete SSM2018?)

[jh.]

> transistor from the collector of the input transistor to the two bases
> reduces this error by another factor of Beta (i.e., 2*In/(Beta^2)).
> Multiplication of current can occur by ratioing the size of the emitters.
> For example, if the "output" transistor of the current mirror has an
> emitter twice the size as the "input" transistor, the output current will
> be twice the size as the the input current. You could also obtain this by
> hooking two transistors in parallel for the output.   Mismatch in the
> emitters will also result in an error - the offset effect.

Aren't there transitors with multiple collectors when you integrate
them in a chip ? Do these have an advantage for current mirrors,
maybe ? (Sharing a common emitter ...)

JH.