A high input impedance single-ended input to balanced differential output amplifier

SPINELLI, ENRIQUE; HABERMAN, MARCELO; GUERRERO, FEDERICO N.; GARCIA, PABLO

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Año: 2020 vol. 69 p. 1682 - 1689

0018-9456

A high input impedance 1 circuit to convert a singleended (SE) voltage to its differential counterpart is proposed.It allows setting the common-mode (CM) output voltage to areference voltage vR while providing gain and a balanced output.The circuit, intended to work as sensor front-end for instru6mentation applications, can be implemented by using availablecommercial devices, thus proving a solution for the board-leveldesign of instrumentation systems. It is based on operationalamplifiers and can be tailored to specific requirements such as lownoise levels, low bias currents, or limited power supply voltages.The CM output voltage is controlled by a closed-loop scheme thatresults in a very good balance between circuit outputs. In orderto test the proposed topology, two single-ended to differentialoutput amplifiers were built and tested: a low-noise amplifierthat presents a noise of 70 nVRMS in a 0.1 Hz?1 kHz bandwidthwith a noise spectral density lower than 2 nV/sqrtHz for higherfrequencies, and a low input bias current amplifier for coaxialpiezoelectric sensors.