Design Of High Gain Wide Bandwidth Rail-to-Rail Operational Amplifier

With the development of society and the progress in science and technology,consumer electronic products are rapidly entering every aspect of our daily life.Under the impetus of the market,the demands for chips with superior characteristics in the integrated circuit domain is higher and higher.As one of the most common and important modules of analog circuit and digital-analog hybrid circuit,the performance of amplifier directly affects the overall performance of the circuit.With the gradual reduction of the power supply voltage,rail-to-rail operational amplifier have become an important developing direction for amplifiers.How to design a rail-to-rail operational amplifier with high gain and wide bandwidth has become a research hotspot.A high-gain wide-bandwidth rail-to-rail operational amplifier is designed by researching and analyzing the literatures of rail-to-rail operational amplifiers at home and abroad,and comprehending the working principle and characteristics of rail-to-rail op amps.The op amp uses a three-stage structure to achieve high gain.The first stage is a folded cascode structure,which uses a complementary differential pair that turns on to ensure rail-to-rail input and constant transconductance.The intermediate stage uses an asymmetric telescopic cascode structure,which can save 1/3 of the power consumption and reduce 1/3 of the layout area for input pair and load with the same input transconductance comparing to the ordinary symmetry telescopic cascode structure.The output stage uses a class AB feedforward output stage to achieve a low quiescent current and low distortion compromise while achieving rail-to-rail output.The design uses a nested Miller compensation with zeroing resistors to construct a left zero to counterbalance the second pole for higher system stability.The reference uses a PTAT current source and a voltage reference source generated based on the PTAT current source.The PTAT current source acts as the tail current source for the op amp input pairs to obtain a relatively constant input stage transconductance as a function of temperature.The voltage reference is used as a reference voltage for the bias circuit to achieve bias voltage.A rail-to-rail op amp with high gain and wide bandwidth is designed on a 0.5?m BCD process and Spectre is used for the simulation platform.With the supply voltage of 2.7 V,the simulation results show that the op amp has achieved an open-loop gain of 146 dB,unity gain bandwidth of 66 MHz,phase margin of 61°,slew rate of 128V/?s,power supply voltage rejection ratio of 107 dB,the common mode rejection ratio of 123 dB,and the rate of transconductance with input common mode range change rate is 7%.The input common-mode voltage range is 0~2.7V,and the output common-mode voltage range is 0~2.7V,which realizes rail-to-rail input and rail-to-rail output.