National Semiconductor Corporation

Jung S Hoei

Donald M Archer

An operational amplifier bias system provides input offset voltage trim current with minimum offset thermal drift. The bias system includes a bias generator that provides bias current to the op amp. Correction circuitry responsive to the bias current provides an input offset trim current that compensates for offset drift error with change in temperature. The correction circuitry includes a resistive element, an input current mirror responsive to the bias current for providing a reference current to the resistive element to provide a temperature coefficient conversion current having a predetermined temperature coefficient, and a voltage reference that sets the resistance of the resistive element.

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Jung S Hoei