Patent ID: 8225659

Claim:
A vibration gyro comprising: a piezoelectric vibration unit including a drive electrode and first and second detection electrodes, the piezoelectric vibration unit being arranged to vibrate in response to a drive voltage input into the drive electrode, and when deformed by a Coriolis force, to generate detection voltages at the first and second detection electrodes, the detection voltages being voltages having a potential difference corresponding to the deformation; an addition circuit arranged to add the detection voltages of the first and second detection electrodes; an automatic gain control circuit arranged to output the drive voltage while performing automatic gain control so that an output voltage of the addition circuit has a given amplitude; a balanced transformerless circuit arranged to output a voltage to the first and second detection electrodes via a detection resistance in a phase obtained by inverting an output voltage of the addition circuit, the voltage having an amplitude greater than amplitudes of the detection voltages; and a detection circuit arranged to detect the potential difference from the detection voltages of the first and second detection electrodes; wherein a circuit constant of the automatic gain control circuit is set so that V agc < V drv ′ × R k 2 × Z + R k , where V agc is the amplitude of each of the detection voltages, V′ drv is a design upper limit value of the drive voltage, R k is the detection resistance, which includes two parallel resistances, and Z is a drive resonant resistance of the piezoelectric vibration unit.