A 3 V 10 MHz pseudo-differential SC bandpass filter using a gain-enhancement replica amplifier

Double-sampling has proven to be suitable for the design of SC filters. Filters are implemented with a simple pseudo-differential common-source amplifier structure. A pseudo-differential approach does not require common-mode feedback loading the opamp differential output, or a tail current source that can limit the positive or negative output swing. This allows reaching the theoretical maximum bandwidth and swing of the opamp. Finally, filters can be realized with a replica amplifier (RA) structure that preserves both the swing and the speed of the main amplifier (MA). A schematic of the complete pseudo-differential opamp circuit is given.