| The integrated circuit technology has developed a lot,the integration has increased a lot since the 21 th century,digital-analog hybrid systems is widely used in the field of electronic information system.With this,new higher requirements coming for the design of analog integrated circuit: high performance,low power consumption,high accuracy,high integration etc.As everyone knows,the performance of operational amplifier,the basic circuit cell of digital-analog hybrid systems,is directly related to the performance of the whole circuit system.Therefore,the research and design of high performance operational amplifier is of great significance and value.In this paper,a high precision,low temperature drift,low power operational amplifier is studied.This operational amplifier has rail-to-rail input,folding common-gate common-source high-gain amplification stage,feed forward class AB rail-to-rail output stage and low input offset voltage achieved using trim technology.All performance indicators are specified to operate in a temperature range from-40°C to +125°C.The operational amplifier input circuit designed in this paper adopts complementary full-differential input pairs to expand the input voltage range,and the bias circuit of input pairs is constant transconductance bias circuit.The trim circuit is added on the input end in order to achieve a low input offset voltage.Trim technology uses a one-time programmable memory.One-time programmable memory cell has an one-time programmable memory based on fuses by fusing the selected unit of fuse array in a set of programming,and a sense circuit which can record fuse programming data,then one can use one-time programmable memory to store fuse data to control trim of the op-amp input differential pairs.The high gain amplifier stage has folded cascode structure.Feedforward AB rail-to-rail output stage is controlled by floating current source,the purpose is to reduce the dependence of AB control circuit on power supply voltage,to reduce the influence of common mode input voltage on static current of output stage,and at the same time the power supply rejection ratio of circuit is improved.Based on 0.25?m CMOS process from a certain wafer fab,the circuit simulation is done under CADENCE software environment.And then the chip is tested and verified at laboratory level including different temperature environments.The final test results of this operational amplifier show that the power supply voltage range of this operational amplifier is from 2.2V to 5.5V.When power supply voltage of 5.5V,typical values input offset voltage is about 25?V,offset voltage temperature drift is less than 0.6?V/°C,quiescent current is about 1mA,typical source current is 23 mA,typical sink current is 22 mA,typical total power dissipation is less than 250 mW,the open loop gain is about 120 dB,unity gain bandwidth is about 10 MHZ,phase margin meets 60°,chip size is 850?m* 950?m,finally complete the design of an operational amplifier,... |
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