Low-voltage CMOS operational amplifiers with wide input-output swing based on a novel scheme

A scheme to achieve low-voltage wide-bandwidth operation of CMOS op amps with rail-to-rail input and output swing and constant gm is presented. It is based on a novel concept that uses a floating voltage controlled voltage source in the feedback path of the op amp in order to keep its input terminals close to one of the supply rails. Postlayout simulations on a 1.2 V rail-to-rail op amp with 13 MHz GB are presented which verify the proposed scheme.