Current mirros in input stages of a power amp (solid state)

[hawkeye2u]

Any one tried this circuitry ( current mirror) for the differential input stage
If so what are the adv or dis adv
I've seen DOUBLE curr mirrors in high quality designs
Any thoughts :?:

[Boofhead]

I'm not sure I undestand the question.  A common configuration is a differential amplifier with a current mirror bridging the two diff-amp collectors.   The advantage is it doubles the current swing and hence doubles the transconductance (gain) of the stage.

[hawkeye2u]

Yes its in the collector circuits of the differential input amplifier
My question is what sort of adv or disadv has this circuit
As I'm understanding it , it greatly improves the voltage driving capacity of the input stage, as it's load is greatly reduced due to the fact that the Collectors ( of the differential input ) are separated from the load by the collectors of the current mirror on the collector circuit, also the currents through the input transistors are VERY closely matched, therefore low dist
:?:

[R.G.]

The real advantages of the current mirror load on a power amp diffamp input are two: (1) it balances the currents of the two transistors in the diffamp, resulting in about a 10:1 decrease in distortion within that stage and (2) it increases the gain from a few hundred up to a couple of thousand.