PRESSURE SENSOR

PURPOSE:To improve power supply fluctuation characteristics while stabilizing sensitivity in measurement by providing a constant voltage circuit in a signal processing circuit and feeding power supply voltage also to a voltage comparator through a constant voltage regulator. CONSTITUTION:Output from an amplifying circuit section 53 is converted through a voltage comparator 55 having hysteresis into a pulse signal which is outputted through a level converter 59. The voltage comparator 55 has input hysteresis width which is determined by the output width of an element in the comparator 55 and corresponds with the voltage of a power supply 2. When the supply voltage is kept constant using a constant voltage circuit 51 and thereby the hysteresis width is kept constant, total sensitivity of the circuit 5 is kept constant and stabilized. Furthermore, fluctuation of power supply 2 due to high slew rate of the converter 59 and high amplitude operation is absorded by the circuit 51 and noise in the circuit 5 is suppressed. This constitution allows highly accurate detection only of pressure fluctuation and frequency of an object with stabilized sensitivity.