Physical quantity sensor

An object of the invention is to provide a physical quantity sensor capable of producing a highly accurate physical quantity detection signal. The physical quantity sensor has an oscillator for converting an externally applied physical quantity into an electrical signal, an oscillation circuit which makes the oscillator oscillate, and a detector circuit for detecting a to-be-detected signal output from the oscillator by using a detection signal output from the oscillation circuit, includes a delta-sigma modulator, preceding the detector circuit, for delta-sigma modulating either one of the detection signal output from the oscillation circuit and the to-be-detected signal output from the oscillator, and for outputting a modulated signal, a variable voltage source capable of varying an output voltage, and a control unit for controlling the output voltage of the variable voltage source, and wherein the delta-sigma modulator performs the delta-sigma modulation by using a feedback signal created based on the output voltage.