DIGITAL POTENTIOMETER-CONTROLLED PROGRAMMABLE INSTRUMENTATION AMPLIFIER
Ya.Yu. Burkovskiy, Yu. F. Zinkovsky · Scientific notes of Taurida National V I Vernadsky University Series Technical Sciences · 2023
The subject matter of the article concerns the schematic designs of instrumentation amplifiers with programmable gains, specifically tailored for digital processing and mixed-signal, measuring instruments, and data analysis systems.The central goal is to design a circuit that efficiently integrates the advantages of existing programmable instrumentation amplifiers, while also offering the capability to adjust the gain through a digital I2C/SPI interface.The research tasks comprised the analysis of current implementations of instrumentation amplifiers with programmable gains, focusing on their inherent strengths and limitations.This analysis was further extended to describe the operational principle of the proposed amplifier, emphasizing the role of the digital potentiometer in setting the gain.The development of a calculation methodology specific to this amplifier and computer simulations of the proposed design were also undertaken to compare its performance against traditional fixed-gain amplifiers.The methods employed in this research incorporated comparative analysis, computer simulations of the proposed schematic solutions, and the formulation of mathematical models for the electronic components used.As per the results, a novel circuit solution was proposed for a compact programmable instrumentation amplifier, which is based on a differential amplifier with a fixed gain, augmented by a programmable digital potentiometer.This proposed solution was evaluated against existing solutions, and calculation method was introduced to calculate the specific parameters of such an amplifier.In conclusions, elements of the calculation method for the programmable amplifier were delineated, facilitating estimations of permissible input voltage levels and discreteness of gain adjustments.The proposed circuit solution exhibits several advantages, such as compactness, adaptability, an extensive gain range, and the ability for automatic gain error calibration.However, a notable limitation is the potential reduction in the common-mode rejection ratio at higher frequencies, attributed to the parasitic capacitance at the gain adjustment input pins.