barefoot
Well-known member
I've designed a class AB buffer than has some fairly nice properties: low distortion, and smooth frequency and phase response roll-off above 10MHz. Now I want to put it inside of a feedback loop, but I'm getting strange results from the simulator.
Here's an example of what I get using the buffer with a NE5532 (the only op amp model I have in my demo software) in a non-inverting configuration. The gain is 12dB and I've adjusted the value of a parallel feedback capacitor to yield the smoothest high frequency roll off with no bumps. But I can never get rid of that positive phase response.
A positive phase response is bad, no? I've tried altering the feedback capacitor as well as the Miller cap, but that just creates more or less of a peak around 7Mhz. The phase response is always positive, no matter what combination I try. The load value doesn't really change things either. Is this a normal and/or stable phase response?
Thanks,
Thomas
Here's an example of what I get using the buffer with a NE5532 (the only op amp model I have in my demo software) in a non-inverting configuration. The gain is 12dB and I've adjusted the value of a parallel feedback capacitor to yield the smoothest high frequency roll off with no bumps. But I can never get rid of that positive phase response.
A positive phase response is bad, no? I've tried altering the feedback capacitor as well as the Miller cap, but that just creates more or less of a peak around 7Mhz. The phase response is always positive, no matter what combination I try. The load value doesn't really change things either. Is this a normal and/or stable phase response?
Thanks,
Thomas