Abstract: The Hall-effect sensor HS' of the invention incorporated in a CMOS integrated circuit IC' is formed with a well 2' as the sensor active layer on a substrate 1'. Heavily doped regions 31', . . . , 34', in the well 2' are connected with sensor metal contacts 41', . . . , 44'. The upper plane S' of the substrate 1' is covered by a field oxide layer 5' the thickness thereof being between 0.8 .mu.m. and 1.0 .mu.m. Over the layer 5' in the region 50' surrounding the sensor contacts 41', . . . , 44', a polysilicon layer 6' is provided to block the disturbing influence of ions migrating in the field oxide layer 5'.

Abstract: A watthour meter or a wattmeter comprising Hall sensors and possessing a precise linearity of the conversion of low voltage into frequency within a broad dynamic range. The required linearity is achieved by providing a multiplication-adding circuit MS with a current output, to which the noninverting input of the last operational amplifier in the circuit is connected, by providing a current-frequency converter IFC with a differential integrator DI comprising an active compensation feedback circuit, by shunting the output and the input of the converter IFC by a compensation circuit CC to compensate the ripple, offset and charge injections of electronic switches, and by placing the Hall sensors so that the magnetic induction direction in the slits of a ferromagnetic yoke is different for each sensor of a pair of them.

Abstract: A wattmeter in which a Hall sensor is provided with a large number of Hall elements, whose voltages are individually tapped. The wattmeter circuit is further provided with an impulse-width modulator, the input voltage of this modulator being periodically reversed, with a feedback to compensate the disturbing voltages, and with a circuit for precision curvature compensation CMOS bandgap reference. The output of an embodiment of the wattmeter is adapted to the reading-off by a computer. A wattmeter can be realized on a semiconductor wafer.