Fontana Bridge
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A Fontana bridge is a type of
bridge circuit A bridge circuit is a topology of electrical circuitry in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them. The bridge ...
that implements a wide frequency band voltage-to-current converter. The converter is characterized by a combination of positive and
negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused ...
loops, implicit in this bridge configuration. This feature allows compensation for parasitic impedance Z_ connected in parallel with the useful load Z_, which in turn keeps an excitation current I_ flowing through the useful load Z_ independent of the instantaneous value of Z_. This feature is of great advantage for making electromechanical transducers. If balance condition: :Z_ Z_ = Z_ Z_ is met, then: :I_ = V_\frac The circuit includes two differential amplifiers. 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. Ordinary operational amplifiers can be adopted with limitations in accuracy and bandwidth. The Fontana bridge is also called Compensated Current Injection Circuit. It was originally discovered by Giorgio Fontana,
University of Trento The University of Trento (Italian: ''Università degli Studi di Trento'') is an Italian university located in Trento and nearby Rovereto. It has been able to achieve considerable results in didactics, research, and international relations accord ...
, Italy, in 2003 using a symbolic equation solver for
Kirchhoff's circuit laws Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirc ...
. The bridge details are available in.


References

Bridge circuits {{electronics-stub