| The sensor is a widely used device that converts environmental variables into voltage or amperage that can be processed by the electronic circuit through sensing external environmental variables.However,in the process of conversion,influenced by process deviation in production environment and device structure,etc.,there exists zero drift and temperature drift of the sensor.Zero drift is mainly manifested in the fact that when the external zero signal is input to the sensor,the output signal of the sensor is not zero,and the temperature fluctuation makes the sensor output error,affecting the signal amplification.When the external environmental variables change very slightly,the change on the sensor will be very small as well,and such signal changes are likely to become unrecognized along with circuit noise in the circuit processing.The instrumentation amplifier works to compensate zero drift and temperature drift of the sensor,and reduce or eliminate the internal noise and offset voltage of the circuit through its own noise elimination technology so as to amplify and process small swing signals.In view of signal conditioning problem of the resistance bridge sensor and the existing non-ideal characteristics of the sensor,in this thesis,a self – zeroing set programmable instrumentation amplifier is designed.With programmable voltage gain,the instrumentation amplifier can automatically zero set the input signal and amend the initial error of the bridge sensor by zero set.Main circuits in the paper can be divided into five parts.The first part is the input coarse zero set circuit,which is the offset calibration circuit specially designed for the over-misalignment of the bridge sensor,and can cope with a wide range of sensor misalignment.In this paper,coarse zero set for the bridge sensor is realized in the automatic zero set process by combining the coarse zero calibration voltage with the automatic zero set circuit.The second part is an automatic zero set amplifier,which is used to zero set the offset voltage and the noise inside the amplifier.The third part is the main amplifier,mainly used for amplifying the signal.The fourth part is the output zero set amplifier,which is the output stage of the instrumentation amplifier and also has the function of automatic zero set.The fifth part is programmable gain resistance.The amplifier used for zero set in the design adopts a fully differential input and output structure,which can effectively reduce common-mode noise.Class AB output is adopted to improve output swing.Meanwhile,the automatic zero set technology of ping-pong structure with double zero set operational amplifier is adopted,making zero set process continuous in one clock cycle and improving efficiency of zero set.The programmable resistance array is adopted to realize the multiple adjustment of gain of instrumentation amplifier.In this thesis,based on 0.35?m CMOS process,design and simulation verification of each module and the whole circuit are completed.Based on Cadence Virtuoso tools,verification of layout design is completed.The simulation results show that the output gain and range of the self-zero set programmable instrumentation amplifier can be adjusted from 4 to 128 times,where the input zero set frequency is 7k Hz,the offset voltage of the input 10 m V is entered,and the output offset is only 7.5?V.Customized coarse offset calibration can be made for the input offset voltage of the sensor,which can meet the application of acquisition and conditioning of front-end signals of a variety of sensors. |
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