A non matching mode constant transconductance rail to rail operational amplifier
Aiming at the constant transconductance of the input stage of the traditional rail-to-rail operational amplifier is affected by the process,a non-matching mode low offset constant rail-to-rail operational amplifier is proposed,which the input stage circuit adopts the maximum current control method.The operational amplifier controls the current of the N input to the tube by monitoring the current of the P input to the tube,so as to achieve the requirement of constant transconductance independent of the process.The output stage combines the active load of the folded cascode with the output stage of the class AB control to improve the voltage gain and increase the dynamic range of the voltage output.The operational amplifier is designed based on DB Hitek 0.18 μm process.The simulation results show that,when the power supply voltage is+2.5 V and-2.5 V,the common-mode input range of the operational amplifier is-2.5-2.5 V,and the dynamic output range is-2.5-2.5 V,the average input offset voltage is 12.7 μV,the open-loop gain is 98 dB,the phase margin is 73.1°,and the bandwidth is 73.1 MHz,the power supply rejection ratio is 90 dB and the common mode rejection ratio is 95 dB,the slew rate is 57.1 μs,and the transconductance change rate is only 4.9%,meeting the requirement of constant transconductance.
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维普
