OPERATIONAL AMPLIFIER WITH INDEPENDENT INPUT OFFSET TRIM FOR HIGH AND LOW COMMON MODE INPUT VOLTAGES

摘要

An operational amplifier provides independent trimming of Vos for both high and low common mode input voltages. The amplifier includes complementary input pairs (MP1/MP2, MN1/MN2), and employs a steering circuit (24) which provides a tail current Itail to one pair when Vcm is less than a threshold voltage Vth, and provides Itail to the other pair when Vcm Vth. The input pairs drive a load stage (14) which includes one or more trim inputs (TRIM1, TRIM2) that enable Vos to be varied with one or more trim signals applied to the trim inputs. A first trim signal generating circuit (26) provides a first trim signal (ΔI1) only when Vcm Vth, and a second trim signal generating circuit (28) provides a second trim signal (ΔI2) to a trim input only whenVcm Vth. This allows the input offset voltages at high and low Vcm to be adjusted independently.