Fontana bridge

The converter is characterized by a combination of positive and negative feedback loops, implicit in this bridge configuration.

The top differential amplifier, whose output is referenced to ground potential, has unitary gain.

The bottom differential amplifier, whose output is referenced to ground potential, has ideally infinite gain.

The Fontana bridge is also called Compensated Current Injection Circuit.

It was originally discovered by Giorgio Fontana, University of Trento, Italy, in 2003 using a symbolic equation solver for Kirchhoff's circuit laws.