Thermal feedback drives sensor bridge simultaneously with constant supply voltage and current

A thermal biasing principle that is especially suitable for bridge sensors is introduced. A double-bridge arrangement, integrated in silicon and implemented in a closed thermal feedback loop, is used to realize a fixed operating point and constant sensor parameters. This approach provides a simultaneously constant supply current and voltage for the sensing bridge under all operational conditions. A brief theoretical consideration of the sensor's dynamic temperature behavior is presented. It is shown that a fixed operating point can be obtained by accurate control of the constant voltage and current supplied to the sensing bridge. The principle of operation of thermal feedback biasing was verified experimentally. This biasing principle can be used to obtain a fixed operating point for different kinds of applications for which a modulating bridge sensor is preferred. The biasing concept presented can be used as a sound basis for making a fully integrated, smart, flow sensor using CMOS technology with integrated signal processing.<
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