US Patent 7089808 Torque sensor for vehicle steering system

A torque sensor for a vehicle steering system includes a voltage boosting circuit, an oscillator, an offset voltage circuit part and a current amplifier. The torque sensor further includes a phase inversion part that outputs an offset voltage and a phase-inverted alternating current voltage which is in-phase with the voltage outputted from said oscillator, a waveform selecting part that rectifies the voltages outputted from said current amplifier and said phase inversion part, and first and second coils that are in series each other and connected at each end thereof to an output terminal of said waveform selecting part and an output terminal of said offset voltage circuit part, respectively.