| 摘要 |
PURPOSE:To enable the construction with limited number of parts by controlling a load driving circuit depending on an output according to the difference in the voltage when a reference voltage is applied to one input of an OP amplifier while a voltage proportional to the impedance of a sensor to the other input thereof. CONSTITUTION:In the normal operation, a voltage divided with a resistance 7 and an impedance and a resistance 16 of a sensor 6 is applied to the base of a transistor 15 to turn it on and a reference voltage divided with a resistance 4 and a resistance 5 is applied to a negative input terminal of an OP amplifier 3. On the other hand, in case of disconnection in the sensor 6 or in a connection wire thereof, the base voltage of the transistor 15 is down to a low level to turn off the transistor 15 and the potential at the negative input terminal of the OP amplifier 3 goes to a high level, which brings the output down to a low level to halt a load driving circuit 2. This system enables a lower cost and a smaller size. |
