| 摘要 |
PURPOSE:To protect an input gate from surging by providing an input protecting circuit having a bipolar transistor TR connected to a bias circuit and a circuit consisting of two diodes whose anode electrodes and cathode electrodes are connected in parallel with opposite polarities. CONSTITUTION:A bipolar TR 1 has a base electrode biased by resistances 2 and 3 so that a certain current flows, and a collector electrode is connected to an input terminal 10, and an emitter electrode is connected to an output terminal 11. The circuit which supplies the bias to the base electrode of the bipolar TR 1 is adjusted by resistances 2 and 3 connected between power terminals 16 and 17. If a surge is inputted to the input terminal 10, the current flows from the input to a power source by a diode 6 in case of a positive surge, and the current flows from the power source to the input by a diode 5 in case of a negative surge. Thus, the bipolar TR 1 functions to limit the current flowing to diodes. |
