volume | PIER Journals

Abstract

In the design of a precision operational amplifier (OPA), cancellation of the input bias current is a challenging issue, which is primarily limited by the current mirror mismatch and the low β value of the PNP transistors. This article proposes a new base current compensation design, which enables zero input-bias-current theoretically. The input stage of the circuit is an active load differential pair with a new common-mode feedback (CMFB) circuit based on the current reuse technique, which can provide a stable common-mode voltage for the amplifier without additional power consumption and area occupation. The proposed OPA is designed in a bipolar process with a core area of 2.85 mm × 1.5 mm. Simulation results show that this OPA achieves a 134 dB open-loop-gain, 50 pA input-bias-current @25˚C, and a low supply current of 0.9 mA, which suggests a concise architecture of the OPA for low offset, low noise, low input bias current, and high gain.

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Dr. Ting Hong

Dr. Wenchang Li

Dr. Jian Liu

Dr. Tianyi Zhang