Lgz Landis Gyr Zug Ag

Beat Furrer

Jacob De Vries

Beat Halg

An arrangement which eliminates or reduces the negative influence of small variations in the charge-carrier concentration of a semiconductor material upon the longterm stability of a magnetic field sensor such as a Hall element is disclosed. In an illustrative embodiment, the arrangement comprises a magnetic field sensor, a voltage/current converter which provides a supply current to the magnetic field sensor, an amplifier connected sequentially downstream of the voltage/frequency converter, and an analog/digital or voltage/frequency converter connected sequentially downstream of the amplifier. The amplifier provides a transmission ratio which is proportional to (1+.delta.n/n) or (1-.delta.n/n) where n is the carge-carrier concentration of the semiconductor material in which the magnetic field sensor is formed and .delta.n is a variation in time of the charge-carrier concentration n. The amplifier comprises an inverting amplifier which is formed using an operational amplifier, a feedback resistor and an input resistor. The amplification factor of the amplifier is proportional to the ratio of the resistance values of the two resistors which are incorporated by diffusion in a semiconductor body near the magnetic field sensor. The charge-carrier concentration in one of the two resistors is preferably identical to the charge-carrier concentration (n) in the magnetic field sensor and the charge-carrier concentration in the other resistor is equal to a multiple of the charge-carrier concentration (n). The factor (1+.delta.n/n) or 1-.delta.n/n) compensates for changes in the output voltage of the magnetic field sensor resulting from the variations in the charge-carrier concentration in the magnetic field sensor.

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Mettmenstetten, Switzerland

Beat Furrer