Detecting circuit which suppresses a drift signal

A detecting circuit for detecting an output of a vibratory gyroscope including a prism-shaped vibrating body and two driving and detecting members formed on a surface of said vibrating body used both for driving to vibrate said vibrating body and for detecting to obtain an output corresponding to a rotational angular velocity, said detecting circuit comprising:

• a summing circuit for outputting a sum of output signals from said driving and detecting members;
• a differential circuit for outputting a difference between said output signals from said driving and detecting members;
• a first synchronous detection circuit for synchronously detecting an output signal of said differential circuit in synchronous with a synchronizing signal;
• a second synchronous detection circuit for detecting an output signal of said summing circuit in synchronous with said synchronizing signal;
• and
• a composite circuit for composing an output signal of said first synchronous detection circuit and an output signal of said second synchronous detection circuit;
• wherein a phase difference between a driving signal applied to said driving and detecting members and said synchronizing signal applied to said first and second synchronous detection circuits is 90 degree.