Abstract:
A circuit for measuring variations in the capacitance of a variable capacr forming part of a sensor includes an oscillator which generates an alternating signal which is supplied to two branches of a detection bridge. The first branch includes the variable capacitor connected in series with a variable capacitance diode. The second branch includes a capacitor connected in series with a variable capacitance diode. A differential stage has each of its in puts connected to the common point of a respective one of the branches. Synchronous demodulation means connected to the oscillator, are connected to the output of the differential stage for delivering a DC unbalance voltage Ve which is injected by a feedback line to the common point of the first branch, thereby continuously balancing the detection bridge.
Abstract:
A mechanical magnitude sensor integrated on silicon, and a method of manufacture. The sensor comprises a bendably deformable conductive blade (4) whose free end (43) constitutes the first plate of a variable capacitor whose fixed second plate (24) is constituted by a conductive zone formed on the silicon substrate. A JFET type structure is formed in the vicinity of the anchor point (41) of the blade (4) with a gate zone (21) situated beneath the anchor portion (41) and with drain and source zones (22, 23) being provided on either side of the gate zone (21) in order to amplify a signal representative of variations in the position of the flexible blade (4). The sensor may be used as an accelerometer or as a pressure sensor.