Feedback & audio amp

[andy_c]

about 2nd and higher order compensation op-amp type amplifiers:
isn't there any way to take profits from changed polarity of inputs for higher frequency? For example run an amp in phase shifter mode, with phase curve similar to amp's internal shift?

By that, do you mean just swap the inverting and non-inverting inputs to buy a 180 deg phase shift at the unity loop gain frequency? If that's whay you mean, I think this would cause a problem with DC stability due to positive DC feedback. But I may be misunderstanding what you're saying.

 

[amplifierguru]

Nice reference jlx.

I was about to suggest ref to Jerald Graeme yesterday but only had the EDN articles to direct to. Should've looked it up on BB web. Incidentally the Fig 8 was my Eidetic amp using a OPA627 front end, with a discrete complementary diff'l, Vas and MOSFET output. I added a zero in the main loop for increased stability/phase margin.

I grew up with his book Operational Amplifiers (pub 1971) with Tobey and Huelsman.

Cheers,
greg

 

[darkfenriz]

Andy
I thought to run non-inverting for LF and for HF when polarities are changed to run inverting. But this probably won't work the way I'd expect.

thanks jcx
It will take me some time though.

regards