I want to drive headphones ranging from 32 ohms up to 600 ohms with 100 mW max and (1-10 mW0 nominal. I picked AD8397 with +/- 12V rails and set up the amplifier in multiple feedback topology low pass filter with gain of 4 (12 dB) and cut off frequency 20 KHz.My DAC valid audio range is up to 3.5 KHz How do I know the circuit is stable? I have a small signal AC analysis on the attached. Do I look at the phase when gain is 0 dB? The phase margin is around 240 degrees roughly (60-(-180)). Did I get it right? Or do I need to calculate the beta and plot the response which I don't know how to do. If not, what is the correct method.
Please see my attachment.
I also followed this website: