Oscillation type inertia force sensor

An oscillation type inertia force sensor comprising:

• an oscillator used to detect inertia force;
• an oscillation circuit unit that supplies a driving signal to the oscillator;
• and
• a detection circuit unit that detects inertia force of the oscillator;
• wherein
• the oscillation circuit unit is a self oscillation circuit of a closed loop with the oscillator defining a resonant element, and includes an automatic gain control circuit that amplifies a monitor signal according to an oscillating state of the oscillator to generate and supply to the oscillator the driving signal;
• the automatic gain control circuit includes:
• an amplification circuit that amplifies the monitor signal;
• a comparison circuit that compares a predetermined reference voltage with a voltage of the monitor signal to output a control signal to control a degree of an amplification factor of the amplification circuit based on a compared result;
• and
• a pulse width modulation circuit that modulates the control signal output from the comparison circuit into a pulse width modulation signal having a frequency higher than a frequency of the monitor signal;
• wherein
• based on the pulse width modulation signal modulated at the pulse width modulation circuit, the driving signal is modulated with an output of the amplification circuit switched between an ON state and an OFF state to control the degree of the amplification factor of the amplification circuit.