Research And Design Of High Precision Integrated Operational Amplifier

With the rise of big data technology and the popularization of 5G applications,people's requirements for the hardware of electronic devices have increased significantly.Highprecision integrated operational amplifiers can improve the resolution of digital-analog hybrid systems and are indispensable in fields such as precision instruments and sensor signal conditioning.Compared with the CMOS process,the bipolar process has faster speed,higher transconductance,better device matching,and is more suitable for making high-precision operational amplifiers.Based on the 4?m 40 V complementary bipolar process and Cadence IC5.1.41 environment,this research designed a single-chip multi-stage coupled op amp and achieved the following results:(1)The PTAT current proportional to the absolute temperature.The PTAT current source was designed to provide an input current to proportional current source and Wilson current source,which can compensate the circuit performance that reduced when temperature rises.In the ±15V power supply and temperature range of-40°C to 125°C,the output reference potential of this module varies linearly between-14.02 V and-14.24 V,and the output reference current varies linearly between 12.33?A and 17.17?A.(2)Design a input bias current cancellation branch to supply current for the input stage transistors,and reduce the bias current to n A level,which can be reduced to p A level after trimming.The input stage uses a fully differential circuit to amplify the voltage,and then converts to a single-ended signal by two emitter followers,with a gain of 74.4d B;the intermediate stage uses common-emitter amplification and negative feedback,with a voltage gain of 63.9d B and a bandwidth of up to 53.6k Hz;the output stage plays a role of voltage follower with a gain of 1.The phase margin of the op amp after frequency compensation is63.34°,which is better in contrast with the 114° that uncompensated.The protection circuit designed to prevent overvoltage and reverse connection can work normally.(3)Use Spectre simulator to simulate the overall circuit and obtain the key performance as follows: open loop voltage gain 138 d B,slew rate 1.06V/?s,unity gain bandwidth 10.05 MHz,common mode rejection ratio and power supply voltage rejection ratio are greater than 145 d B,the input offset current is 0.03 n A,the input offset voltage and drift are 9.58?V,0.18?V/?,and the maximum equivalent input noise voltage density at 1k Hz frequency is 10.15 n V,the maximum equivalent input noise voltage within 0.1Hz to 10 Hz frequency is 65.55 n V/?Hz.The performance of the design meet high-precision index requirements.(4)The layout designed in Virtuoso has been verified by DRC and LVS,and the size of it is 2.3mm×2.3mm,which can be accommodated by most packages.