| 摘要 |
PURPOSE:To obtain a protective circuit with voltage limiting effect both in the positive and negative directions by a method wherein two diodes are connected in series in the transistor circuit connecting Zener diode between collector and base. CONSTITUTION:One end of Zener diode 6, collector of transistor 7 and one end of diode 8 are connected to terminal 1 while emitter of transistor 7 and the other end of diode 8 are connected to terminal 2. Then the other end of Zener diode 6 and the base of transistor 7 are connected to constitute a protective circuit. When said circuit is connected to an element 3 to be protected, and the terminal 1 is supplied with positive surge voltage, the voltage between the terminal 1 and 2 is limited by the Zener voltage of Zener diode 6 and the voltage between emitter and base of transistor, while if the terminal 1 is supplied with negative surge voltage, the voltage between the terminals 1 and 2 may be limited by the voltage in the forward direction of the diode 8 protecting the element 3. |
