PURPOSE: To prevent the destruction of output transistor due to the anomaly of power voltage by interrupting the output transistor when collector voltage exceeds predetermined value by the constant monitoring of the collector voltage of output transistor.
CONSTITUTION: The collector of the transistor 4 for protection is connected to the base of the output transistor 2, and also the emitter of the transistor for protection is connected to the emitter of the output transistor. And, the constant voltage diode 5 is connected in the reverse direction to between the collector of the output transistor and the base of the transistor for protection and voltage is set up so that the sum of the voltage between the base and emitter of the transistor for protection and the Zener voltage of the constant voltage diode is higher than the power voltae of the transistor circuit. Thus, when the power voltage exceeds the specified value, trans- loaded output transistor is made OFF and therefore the output transistor can be protected.
SHIMIZU HIROAKI
NAKASHIMA MASAHIKO
| JPS44604B1 |