An operational amplifier (1A or 1B) includes a translinear transconductance stage (2B or 2C) receiving an input signal (Vin) of the operational amplifier and operative to produce a first current (ID18) having a square-law relationship to the input signal (Vin) and a folded cascode operational amplifier (3B) including a differential input stage coupled to receive the input signal (Vin), a folded cascode stage coupled to the differential input stage, and a class AB output stage (45) coupled to the folded cascode stage. The differential input stage includes a tail current source (34) coupled to the translinear transconductance stage and operative to produce a square-law tail current (ID34) scaled to the first current (IDI8) to provide a substantially constant input transconductance for a relatively large range of magnitudes of the input signal (Vin).