Used In Fully Differential Op Amp Pipelined Adc

Since integrated circuits were invented in the fifties of last century, integrated circuits are developed with amazing speed throughout the past few decades. The theoretical basis for the circuit structure and the manufacturing process undergoes great changes, and now integrated circuits have in-depth application in every aspect of people's lives.Operational amplifier is designed for converting analog voltage to digital signal and finishing operation such as add, subtract, multiply and divide initially. But it becomes the most popular module in analog IC design and is widely used in many analog systems especially mixed-signal systems today. In the development process, the design of op-amp is changed from the beginning of the general type to custom-made for different application environments. The paper discusses the circuit structure, performance and test method of the fully differential op-amp which has high slew rate. On the basis of traditional fully differential op-amp, a new BiCMOS differential op-amp is designed out for higher open-loop DC gain, unit gain bandwidth and slew rate which is more suitable for application in pipeline ADC.The paper firstly analyzes the main indicators of op-amp, and a few classic op-amp structures are analyzed and compared. And then a BiCMOS differential op-amp is designed for application in pipeline ADC. In the circuit design process, the designed op-amp achieves better open-loop DC gain, unity-gain bandwidth and slew rate compare to folded cascode fully differential op-amp.Based on 0.6μm BiCMOS process model, op-amp designed in the paper is simulated by the tools of Specture, in the Cadence software environment. In the normal environment, the operational amplifier has DC gain of 101.59dB, unity-gain bandwith of 311.9MHz, phase margin of 63.1°, slew rate of 1379.5 V/μs with consuming only 27.35mW . The area of the operational amplifier is 380um×326um .The simulation results show that the designed BiCMOS fully differential op amp satisfy the expected set of performance indicators, and the circuit has been successfully applied in 12-bit 10Mhz Pipeline ADC in the MDAC switched-capacitor amplifier.