Systematic Approach for the Linearization and Readout of Nonsymmetric Impedance Bridges

This paper presents a general concept for the linearization of impedance bridges with circuit components changing in only one polarity. A feedback loop using a transadmittance amplifier, which is properly designed and matched to the nominal value of the bridge components, reduces nonlinearity from 9% to 0.4% over plusmn20% of bridge imbalance. The method can be applied for dc or ac bridges, and the linearization can conveniently be integrated with the readout circuit, resulting in a highly linear sensor readout. In addition to the linearization of the bridge transfer function itself, the method can be applied for the linearization of a range of transducers with a hyperbolic transfer function