A low-noise, high-precision operational amplifier
Long Zou, Jing Zhang · 2025
This paper presents the design and implementation of a high-precision, low-noise operational amplifier. To address the issue of input bias current caused by the base current of the input differential pair transistors, a novel base current compensation technique is proposed. This method effectively suppresses the input bias current by accurately compensating for the base current of the input stage, thereby enhancing the current driving capability of the differential pair. Consequently, the collector current of the input transistors can be increased to reduce thermal noise, leading to a lower equivalent input-referred noise voltage. The proposed approach achieves superior overall input-referred noise performance. The design is predicated on a 180nm BCD process, and simulation results indicate that the chip exhibits an out-of-regulation voltage of 7.88 μV. The measured input base current of the amplifier with base current cancellation is 12.2 nA. The voltage noise density at 1 kHz has been measured to be 4.5 nV/√Hz.