Method for Reducing the Zero Level of Gallium-Arsenide Operational Amplifiers Based on “Folded” Cascodes without Current Mirrors

We propose method of constructing operational amplifiers (Op-Amp) with a low level of the systematic component of the zero offset voltage (VOS), which can be realized on wide-gap semiconductors (GaAs, GaN, SiC). An example of an Op-Amp circuit for a combined GaAs process technology that allows the creation of p-n-p bipolar and nJFet field-effect transistors only is presented. The Op-Amp circuits under consideration do not contain current mirrors, but have relatively low VOS values. The mathematical analysis of the numerical values of VOS is performed. It is shown that VOS depends on the conditions of relative compensation of the main components of static currents in the Op-Amp high-impedance node and the steepness of the input stage gain. The results of computer modeling of Op-Amp on models of gallium-arsenide transistors show significant advantages of the developed circuit solutions in terms of voltage gain and VOS in comparison with classical methods of Op-Amp design.