| 摘要 |
PURPOSE:To prevent a back-flow through a regulator IC of surge currents, and to obviate the breaking of the regulator IC and the breaking of a semiconductor integrated circuit by connecting emitters in both P-N-P and N-P-N transistors to an external terminal for an input or an output for the semiconductor integrated circuit. CONSTITUTION:When surges at positive voltage are applied to an input terminal 6, a P-N-P transistor 2 is turned ON, and surge currents flow through a negative power supply terminal 5 from a collector in the transistor 2. The input terminal 6 is clamped at VCC+VBE(P-N-P) at the time. When surges at negative voltage are applied to the input terminal 6, an N-P-N transistor 3 is turned ON, and surge currents flow through a collector in the transistor 3 from a positive power supply terminal 4. The input terminal 6 is clamped at -VSS-VBE(N-P-N) at that time. Accordingly, surge currents do not flow back to each power supply terminal, and reverse currents do not flow through a power circuit for an IC regulator, etc. connected to several power supply terminal. |
