u/FutureAd1004

I am designing a fully differential OTA with a low supply voltage (800mV) and a relatively large differential output swing (400mV). I initially implemented with the differential pair based CMFB (shown in the figure, which is from here), but its input range is insufficient for a 400mV swing. To make matters worse, the OTA's output common-mode current varies during operation, making the diff-pair CMFB even more unreliable. I have considered using resistive sensing, but the OTA's high output impedance makes loading a significant concern. Does anyone have suggestions for a CMFB architecture that could work in this scenario?