A crystal resonator area and side electrode shieldingformation blocks thereabout are formed on a crystal substrate through etching with both areas kept separate from each other with a gap. Both transistors operate in the same operation conditions except that the second transistor has a smaller channel width in comparison with that of the first transistor. Even in the event of the abnormality in any unit, each unit is stopped nearly simultaneously, so that the filling system can prevent damage and the like to the unit.