Gallium Arsenide Operational Amplifier Based on a “Folded” Cascode Containing No Current Mirrors

The authors proposed and described the gallium arsenide (GaAs) operational amplifier (Op Amp) circuit engineering solution. This architecture is implemented on the basis of combined tech processes, including junction field-effect transistors with n-type channel and bipolar junction p-n-p transistors. It is worth considering that such an element base complicates the design and synthesis of precision Op Amp circuits due to the absence of bipolar junction p-n-p transistors in the specified tech process. A considerable advantage of the offered Op Amp, which is made without including current mirrors in its architecture, is the use of a so-called “folded” cascode sub-circuit in the intermediate stage with an unconventional circuit for establishing its static, ensuring minimization of the offset voltage systematic component ($\mathrm{V}_{\mathrm{OS}}$). Low noise is achieved by using n-channel input junction field effect transistors. The computer modeling results of GaAs OpAmp statics, as well as logarithmic amplitude-frequency characteristics are presented in the article, which show that the voltage gain of the specified Op-Amp exceeds 70 dB, and V
OS
has a value of about $145 \mu \mathrm{V}$ (it should be noted that the studies have been carried out without any analysis of the technological variation of the parameters of the n-JFETs and p-n-p BJTs in use.).