| 摘要 |
PURPOSE:To provide a stable and reliable pressure detection circuit so as to improve the detection reliability of jammes foreign matters. CONSTITUTION:A first operational amplifier 10 subjected to negative feedback is made from a pressure sensitive sensor 11 the resistance of which changes in accordance pressing forces, a transistor 14 the collector of which is connected to the inverts input terminal of the amplifier 10 and the resistance value R0 of which between its collector and emitter changes in accordance with the forward voltage (control voltage) between its emitter and base, and the output terminal of the amplifier 10 is connected an inverted input terminal. Then a reference voltage source 17 connected to a noninverted input terminal and second operational amplifier 16 which applies a control voltage across the base of the transistor 14 through a time constant circuit 21 are provided. |
