Design of a high common-mode voltage differential amplifier
In response to the demand for localization of differential amplifier chip,this paper introduces a ±120 V common-mode input voltage integrated differential amplifier with high Common Mode Rejection Ratio(CMRR)based on the 40 V bipolar process with metal thin film resistors.The article covers the basic principles and structural components of differential amplifiers,and analyzes the difficulties in the design process of differential amplifiers,including common-mode rejection ratio,input offset current and gain error.The methods to improve the CMRR and lower input offset current are introduced which are the technologies of integrated metal thin-film resistors trimmed by laser cutting and the modified base current compensation configuration,and improved Darlington tube is used to increase the open-loop gain of the amplifier and reduce the gain nonlinearity of the amplifier.The overall chip size is 2.82 mm ×2.02 mm,the dual power is±15 V,and the current consumption is 1.36 mA.Experimental results show that,at supply voltage of±15 V,the CMRR is 85 dB and the input offset current is only 84 pA with 98.4％compensation precision,and the gain error is 0.02％.
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维普
