The method of the errors calculation from the input common-mode signal in the analog interfaces based on the differential difference operational amplifiers and the ways of their decrease

Abstract

The article suggests a new method of the errors evaluation from the several common-mode signals in the differential difference operational amplifiers (DDAs), based on the theory of autonomous multiport circuit. These errors of DDA in its main connection circuits can be described by feeding a special current autonomous parameter to the classical equivalent circuit of DDA. This parameter is connected with the high-impedance node of DDA and depends on the level of the common-mode components in the inputs of some input differential stages and also on the parameters spread of the elements. The paper shows that in DDAs the common-mode rejection ratio (CMRR) significantly worsens in comparison with classical op-amp. The parametric and circuitry methods of CMRR increase in the DDAs based on the inherent compensation of parasitic impedances are considered.