C o mp ac t CMO S Constant-gnz Rail- t o-Rail Input Stag e with gTTl-Clontrol by an Electronic Zener Diode

Abstract-A family of:ompact CMOS rid-to-rail input stages with constant-g, is preslmted. To attain a constant-g, over the whole common-mode in1 but range, an electronic zener diode is inserted between the ta Is of the complementary input pairs. This zener keeps the slim of the gate-source voltages of the input pairs, and therefore the gm of the rid-lo-rail input stage, constant. Two possible il nplementations of the zener have been realized and inserted in a rail-to-rail input stage. These input stages are implemented ir two two-stage compact amplifiers. Both amplifiers have been realized in a 1 pm BiCMOS process. They have a unity-gain frequency of 2-MHz, for a capacitive load of 20 pF, I