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 loops, implicit in this bridge configuration. This feature allows compensation for
parasitic impedance connected in parallel with the useful load
, which in turn keeps an excitation current
flowing through the useful load
independent of the instantaneous value of
. This feature is of great advantage for making electromechanical transducers.
If balance condition:
:
is met, then:
:
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, 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 Kirchhof ...
. The bridge details are available in.
["Compensated Current Injection Circuit, theory and applications" Giorgio Fontana - Rev. Sci. Instrum. 1332-1337, 74 (3), March 2003.]
ArXi
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References
Bridge circuits
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