Zhiyuan Li Mingyan Yu Jianguo Ma A Rail-to-Rail I/O Operational Amplifier with 0.5% gm Fluctuation Using Double P-channel Differential Input Pairs. 563-568 2006 conf/vlsid/2006 VLSI Design http://doi.ieeecomputersociety.org/10.1109/VLSID.2006.23 db/conf/vlsid/vlsid2006.html#LiYM06