Research And Design Of Complementary Bipolar Instrumentation Amplifier With Low Offset And High CMRR

With the development of microelectronics technology and embedded design,more and more applications need to detect and measure some weak amplitude signals.These weak amplitude signals need to be properly amplified while suppressing the interference signal.To overcome this problem,instrumentation amplifier is used to suppress any undesired noise or common mode signals that affect the original signal.And it also provides appropriate amplification of the desired signal.Therefore,it is of great significance to study the instrumentation amplifier with low offset and high Common Mode Rejection Ratio(CMRR).In thesis,HX30 bipolar process is used to realize the instrument amplifier structure based on the traditional three operational amplifiers structure.The circuit design,presimulation,layout and post-simulation are carried out.The core circuit module includes bias circuit,two in-phase amplifier circuits and a differential amplifier circuit.In the most of existing literatures,three operational amplifiers of the three operational structure instrument amplifiers have the same type and structure.In this paper,the gain stage and output stage circuits of in-phase amplifier and differential amplifier are the same,but the input stage is different.The input stage of in-phase amplifier adopts current transmission structure,and the differential amplifier adopts differential transconductance input structure.Compared with the traditional three operational amplifiers,the instrument amplifier designed in this paper has made great improvements in CMRR,offset voltage,gain and bandwidth.The output terminals of the three operational amplifiers all adopt the rail to rail output structure,which makes the instrument amplifier have the output swing similar to the rail to rail.In order to achieve the desired CMRR,low offset voltage,low noise and so on,the appropriate operational amplifier topology is selected.In addition,the main parameters of offset voltage,temperature drift and CMRR which affect the whole structure of the instrumentation amplifier are analyzed.In order to get highprecision instrumentation amplifier,laser trimming technology is used to the peripheral resistance network,which needs to be matched to instrumentation amplifier.The whole instrument amplifier circuit is simulated by the spectre tool of Cadence,and the process is HX30 complementary bipolar process of Yu Xin company.The simulation results show that the instrument amplifier can work normally in the range of3 V ? 9V for single power supply,and can work normally in the range of±3V?±9V for dual power supply.The typical input offset voltage of the amplifier is 152.3?V.The temperature drift is 1.69?V/?,and the Common Mode Rejection Ratio Ratio(CMRR)is greater than 84 d B.The equivalent input noise is 37 n V/?Hz at 1k Hz,the gain can be adjusted in the range of 1 ? 1000,the gain error is 0.0232%.And the bandwidth under unit gain is about 950 KHz,and the current consumption is 450 u A when 5V single power supply is used.This instrumentation amplifier in this paper can be used in low power medical instrument,sensor interface,thermocouple amplifier,industrial process control,low power data acquisition and other fields.