Resistive-Free Reference Current Sources and Dynamic Loads for High-Temperature Operational Amplifiers on Wide-Gap Semiconductors

The basic functional units of high-temperature operational amplifiers (OAs) based on wide-gap semiconductors (GaAs, SiC, GaN, etc.) are considered. Their basic functional units include resistance-free GaAs JFet two-terminal reference current elements that set the static mode of the input differential stage (DS) in the range of 0.08-2mA, and JFet dynamic loads with an internal resistance of 0.03-1.2M$\Omega$ both in the drain circuit and in the source circuits that determine the voltage gain of the DS. In the LTspice software, we investigated an GaAs OA circuit that does not contain integral resistors, the functions of which are performed by dynamic loads on the JFet with different channel widths. It is shown that the proposed OA circuit solutions are characterized by a low magnitude of the systematic part of the zero offset voltage.