Low-Voltage CMOS Operational Amplifiers: Theory, Design and Implementation discusses both single and two-stage architectures. Opamps with constant-g_m input stage are designed and their excellent performance over the rail-to-rail input common mode range is demonstrated.
The first set of CMOS constant-g_m input stages was introduced by a group from Technische Universiteit, Delft and Universiteit Twente, the Netherlands. These earlier versions of circuits are discussed, along with new circuits developed at the Ohio State University....

Low-Voltage CMOS Operational Amplifiers: Theory, Design and Implementation discusses both single and two-stage architectures. Opamps with constant-g_m input stage are designed and their excellent performance over the rail-to-rail input common mode range is demonstrated.
The first set of CMOS constant-g_m input stages was introduced by a group from Technische Universiteit, Delft and Universiteit Twente, the Netherlands. These earlier versions of circuits are discussed, along with new circuits developed at the Ohio State University....