A High-voltage Op Amp Design

The first chip of integrated circuits of the world was made in the U.S. in 1959.In the followed 50 years,the design technology of integrated circuits has been developed enormously. As the nuclear module of the unit of analogue circuits,people pay more and more attention to it. Man has achieved greate progress in design of the low voltage operational amplifier.But in design of high voltage operational amplifier, there is less progress in the field of high voltage than in that of low voltage because of the limit of high voltage craft and the affect of removing heat.In recent years,in some field of high voltage appliance,such as motor control system, piezoelectricity sensor and the drive circuits in printers there is emergent need of high voltage operational amplifier.Thus it is a pressing task to design high voltage operational amplifer with good feature.The writing of my thesis is just focused on above problem.By hard studing the principle of operational amplifier and the endureness to high voltage and BCD and SOI high voltage craft,and through the employment of the Xfab craft of Germany ,a kind of double high voltage operational amplifer used in piezoelectric sensors and the computers and the interfaces of vacuum tube is designed in this thesis.The power voltage of amplifer is±175V,the output current is 60mA,the DC voltage gain is 106dB,the slew rate is 40V/uS and the power is 200mW.MOSFET output makes the high voltage amplifier to avoid the second breakdown limitation,it's power dissipation keeps the minimum,the quiescent quota current of each amplifier is only 2 mA.The suitable structure is applied according to demand of the ircuit.In the first stage,the structure of double input port and one output port is applied,and four diodes are used to protect the import circuit.In the second stage,the common source circuit is applied,and the constant current source is used to be source load to prove the voltage gain.The push-pull common drain amplifer of class B is used in the output stage,and it's giggest efficiency can be 78.5%.Thus the main circuit is complished.In addition ,in order to enhance the stability of the circuit in higher frequency and temperature,the method of out miller compensation and out feedback is taken.In the last part of the thesis,some important parameters such as DC voltage gain ,the phase margin and slew rate are analyzed and inferred carefully,and the general simulation to the circuit has be made by using the analogue design tools of Cadence in the SUN work platform,the results of simulation meets to and surpluses the demands of the circuit.Hence the design of the project has been accomplished successfully.