Patent ID: 7155985

Claim:
A torque sensor for a vehicle steering system comprising: a voltage boosting circuit that boosts a voltage supplied from a power source; an oscillator that oscillates with the boosted voltage from the voltage boosting circuit; a current amplifier that outputs a DC voltage and an AC voltage having a phase equal to that of the output voltage of the oscillator; an inverting current amplifier that outputs a DC voltage and an AC voltage having a phase opposite to the phase of the output voltage of the oscillator; first and second coils, each of which is connected to one of an output terminal of the current amplifier and an output terminal of the inverting current amplifier, respectively, the first and second coils connected in series to each other; first and second resistors that are connected in parallel to the first and second coils, the first and second resistors connected in series to each other; a first differential amplifier that is supplied with the voltage of a node between the first and second coils and with the voltage of a node between the first and second resistors, the first differential amplifier differentially amplifying the supplied voltages; a first sampling pulse generator that generates a sampling pulse synchronized with the output voltage of the oscillator; a first synchronous wave detector that detects the AC voltage output from the first differential amplifier in synchronism with the sampling pulse output from the first sampling pulse generator; a first sample-and-hold circuit that samples and holds the voltage output from the first synchronous wave detector; and a first voltage-current converter that converts the voltage output from the first sample-and-hold circuit into current and outputs the current as a torque signal.