| 摘要 |
PURPOSE:To prevent the titled circuit from being destroyed by inserting a diode to an emitter of an NPN transistor (TR) of complementary push-pull coupling using the NPNTR and a PNPTR so as to prevent an excess current at short- circuit from being generated. CONSTITUTION:The diode is provided between a resistor and the emitter of the NPNTR and the diode is provided between the cathode of the former diode and the collector of the TR in the complementary push-pull connecting circuit where the NPNTR7 and the PNPTR10 are employed, and then the circuit current at short-circuit of output terminals is limited surely. For example, even when the output terminal comes to contact a power supply terminal in the push-pull connecting circuit, since a breakdown voltage of the diode 15 is as very high as several volts, no breakdown takes place. Then a current I3 is zero. Current limit is applied at the short-circuit of the output circuit through the negative feedback action of a current amplification factor hFE10 of the PNPTR10. |
