关键词: 模拟集成电路, 双极型运算放大器, 差分放大器, 高精度, 低失调

Abstract: Differential pair structure, as the basic structure of operational amplifiers, is critical to circuit performance.In reality, process deviations cannot be avoided, and the mismatch they bring can affect the accuracy of the operational amplifier. For multi-stage operational amplifiers, the degree of detuning of the input stage determines the accuracy of the whole amplifier, so the low-offset input level has become one of the key points of operational amplifier design.In order to get a low-offset operational amplifier input stage, the relationship between differential pair resistor R_C and circuit mismatch is studied, and the effect of the remaining mismatch term is compensated by trimming the mismatch resistor ΔR_C.The overall chip parameters verification is realized in the process XY 4 μm 50 V. The result shows that the offset voltage is below 60 μV, which is 76% less than the general operating amplifiers. The temperature drift coefficient can reach 0.3 μV/℃, which is 50% less than the general operating amplifiers. This method is simple and convenient, avoids large-scale adjustments in the circuit structure,the impact on circuitpower consumption can be ignored.

Key words: analog integrated circuit, bipolar operational amplifiers, differential amplifier, high precision, low offset