Torque sensor for vehicle steering system

A torque sensor for a vehicle steering system, comprising:

• a voltage boosting circuit that boosts voltage provided from a power source;
• an oscillator that oscillates by receiving boosted voltage from said voltage boosting circuit;
• an offset voltage circuit part that generates an offset voltage by using said voltage of said power source;
• a current amplifier that outputs an offset voltage and an alternating current voltage which is in-phase with a voltage outputted from said oscillator;
• a phase inversion part that outputs 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;
• 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;
• first and second resistances that are in series each other and connected in parallel to said first and second coils;
• first and second peak detecting parts that detect peak values of voltages of a contact part between said first and second resistances and a contact part between said first and second coils, respectively;
• a first differential amplifier that executes differential amplification by receiving voltages outputted from said first and second peak detecting parts;
• and
• a first voltage-current converter that outputs a torque detecting signal by converting voltage, which is outputted from said first differential amplifier, into a current.