R. Hogervorst et al., COMPACT CMOS CONSTANT-G(M) RAIL-TO-RAIL INPUT STAGE WITH G(M)-CONTROLBY AN ELECTRONIC ZENER DIODE, IEEE journal of solid-state circuits, 31(7), 1996, pp. 1035-1040
A family of compact CMOS rail-to-rail input stages with constant-g(m)
is presented. To attain a constant-g(m) over the whole common-mode inp
ut range, an electronic zener diode is inserted between the tails of t
he complementary input pairs, This zener keeps the sum of the gate-sou
rce voltages of the input pairs, and therefore the g(m) of the rail-to
-rail input stage, constant. Two possible implementations of the zener
have been realized and inserted in a rail-to-rail input stage, These
input stages are implemented in two two-stage compact amplifiers. Both
amplifiers have been realized in a 1 mu m BICMOS process, They have a
unity-gain frequency of 2-MHz, for a capacitive load of 20 pF.