Circuit Design of CJFET OPA Based on the Differential Stage with a Slope Multiplier

The paper proposes the differential stage (DS) scheme based on field-effect transistors with a control pn-junction (JFET), which has an increased gain slope when the JFET operates in microcurrent mode. Examples of its practical use in the structure of a low-temperature operational amplifier (OPA) are given. The results of computer simulation in the LTSpice XVII environment are presented, which show that the proposed circuitry techniques for constructing JFET DSs provide an increase in the value of the open-loop gain OPA (up to 120÷135 dB) in a wide temperature range (from 27°C to −197°C) and low values of the systematic component of the zero offset voltage (less than 180 µV). The considered OPA structures can be used due to their implementation on JFET in low-noise analog interfaces for processing sensor signals in automation devices operating in harsh operating conditions.