TEMPERATURE-INDEPENDENT AMPLIFIER OFFSET TRIM CIRCUIT

摘要

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 (MPl) having a gate, and a second correction FET (MP2) 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 (MNl, MN2). A resistor (R2) 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 (MN3) 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.