Resolver signal processing circuit

A resolver signal processing circuit for amplifying two phase signals output from a resolver attached to a motor, the resolver signal processing circuit comprising:

• a differential amplifier;
• a plurality of resistor groups connected between the resolver and the differential amplifier and configured to vary a voltage input from the resolver to the differential amplifier in response to a diagnostic signal applied thereto, each of the resistor groups including resistors and switches;
• and
• a control unit configured to determine a rotation angle of the motor based on an output signal of the differential amplifier, determine a short-circuit state including a short-circuit in the resolver, a short-circuit of the signal input path to a power supply and a short-circuit of the signal input path to a ground, and control on-off states of the switches in the plurality of resistor groups to vary resistances of the plurality of resistor groups and thereby vary an input voltage range of the differential amplifier in correspondence to a determined short-circuit state.