An operational amplifier having temperature-compensated offset correction.
The amplifier includes an operational amplifier circuit, that has a first
input field effect transistor (FET) having a gate connected to receive a
first input signal, and a second input FET having a gate connected to
receive a second input signal, the first and the second input FETs being
connected together to receive a first bias current, and also being
connected to respective sides of a first current mirror. A correction
amplifier circuit is also provided, that has a first correction FET
having a gate, and a second correction FET having a gate, the first and
the second correction FETs being connected together to receive a second
bias current, and also being connected to respective sides of a second
current mirror. A resistor is arranged to have a fixed voltage provided
across it, one terminal of the resistor being connected to the gate of
the first correction FET and the other terminal of the resistor being
connected to the gate of the second correction FET. A first bias FET is
connected to conduct an "extra" current from the second correction FET
that is blocked by the current mirror action from flowing through the
second current mirror. A second bias FET is connected in current mirror
configuration with the first bias FET to form a third current mirror, and
is configured to mirror and scale the current through the first bias FET
to a selected one of the first input FET and the second input FET.