Bessel-like compensation of three-stage operational transconductance amplifiers

In this paper, we introduce a simple and well-defined approach for the design of fast settling amplifiers suitable for switched-capacitor circuits and characterized by low capacitive loads, in the order of few pico-farad. In the specific, the design is based on a new Bessel-like compensation that sets the phase of the closed-loop amplifier to be linearly related to the frequency, thus emulating the behavior of an ideal delay, like in a Bessel filter. The proposed Bessel-like approach is validated through the design and the simulation of two 3-stage amplifiers in a 65-nm CMOS process.