Low-Temperature JFET OpAmp Based On a Folded-Cascode with High Static Regime Symmetry of Transistors That Determine the Systematic Constituent of the Offset-Voltage

The original architecture of operational amplifiers (OpAmps) implemented on complementary JFETs or depletion-mode complementary MOS is considered. The feature of the proposed OpAmps is differential input stage and folded-cascode special designs, which have a high symmetry of the FETs static regime from terms of gate-to-drain voltages. Computer-based simulations of the OpAmp in the LTspice-XVII was conducted between -197 and 27 degrees Celsius. The proposed circuit solutions reduce the systematic constituent of the offset-voltage (up to 10 $\mu \mathrm{V}$) and increase voltage gain (up to 87 dB) of the open-loop OpAmp. The explored OpAmps are recommended by the authors of the article for analogue, including low-noise, and analogue-to-digital devices, for example, active filters, comparators, actuators, and others, which are used in systems of communication and management, such as at cryogenic temperatures, and/or under radiation conditions.