Current Mirrors (simple one vs. improved wilson)

[Lee Knatta]

Hi all

Trying to understand Anthony's AV series amps an idea came into my mind I like to share with you. Maybe it's rubbish, maybe an improvement.

I noticed in most amps the simple 2 transistor current mirror is used:

Current mirror - Wikipedia, the free encyclopedia

Maybe the 4 transistor improved Wilson current mirror could be an upgrade:

Wilson current mirror - Wikipedia, the free encyclopedia

I already searched the forum and read some topics but was not able to answer this question myself.

I simulated the amp with both current mirrors in VAS and the improved Wilson performed a little bit better. (I'm not good at Spice and circuit design.) Maybe the Wilson CM has serious drawbacks and isn't recommended for amps? Maybe it offers advantages?

Any input is highly appreciated.

Thanks.
Lee

 

[richie00boy]

Well it becomes a trade of complexity against results. The simple mirror gives huge improvement over resistive load, the extra performance of the Wilson is not such a great leap.

 

[ontoaba]

There are many type/ways of current mirroring, LM13600 or CA3080 as transconductance opamp for example, high precision current mirroring added everywhere.

 

[Lee Knatta]

Well it becomes a trade of complexity against results. The simple mirror gives huge improvement over resistive load, the extra performance of the Wilson is not such a great leap.

Thank you for your reply.
The extra performance seems to be a very little leap. I simulated about 0.001% THD improvement. Maybe not worth two extra transistors.
But maybe there's more improvement in a real circuit with less ideal components, not perfectly matched transistors, temperature changes, not equal temperature in all parts and so on...?

Thanks
Lee