PURPOSE: To prevent a transistor (TR) from being damaged because of a positive/negative surge voltage or a high voltage, by connecting a diode and a Zener diode connected in series to the TR in parallel.
CONSTITUTION: Figure shows a circuit protecting a TR4 against a positive surge voltage by providing the Zener diode 8 and the diode 9. A surge current 7 flows to the Zener diode 8 and the diode 9 with the positive surge voltage generated through the effect of a load 3, allowing to prevent damages of the TR4 due to the positive surge voltage. In this case, it is required to increase the sum of an operating voltage VZD1 of the Zener diode 8 and an operating voltage VD2 of the diode 9 more than an output voltage. Further, through the connection of the Zener diode and the diode connected in series with an external terminal of an LSI or a transistor AMP output stage, the performance of the LSI is not deteriorated.
KAJIWARA SHINJI
MOTOI HIDESUKE
| JPS4912847B1 | 1974-03-27 |