A Low Noise Precision Operational Amplifier

A low noise precision operational amplifier is presented in this paper, which has the advantages of low offset and low noise for high precision, high resolution and low error applications. The design was fabricated with a 40V bipolar process. The input stage of the circuit is a resistive load differential pair with an input bias current compensation structure. The second stage is a common-emitter structure in the middle. The output stage is complementary push-pull structure. When power supply is ±15V, measured results show that slew rate of the OPA is 0.3V/μs, it gets an open loop gain of 132dB with a supply current of 1.7mA and an input bias current of 2nA, the equivalent input noise is only 8nV/√(Hz), and the area is about 2.3mm×1.6mm.