| 摘要 |
PURPOSE:To improve the short circuit resistance value of transistors (TRs) under load-shorted status by connecting the 2nd TR between the base and emitter of the 1st TR and controlling the base driving current of the 2nd TR by a diode to reduce the collector current of the 1st TR. CONSTITUTION:To branch the base driving current of a TR20, a TR5, a diode 6 and a resistor 7 are added. When base driving current source output current IB shown in Fig. (a) is made to flow from a base driving current source 3 to the base of the TR20 under a point t1 of time immediately after the short of a load 4, large short current is made to flow into the collector of the TR20. At that time, the voltage VBE between the base and emitter of the TR20 is also raised by base-emitter saturation voltage/collector current characteristics shown in Fig. (c). If said voltage exceeds the forward voltage drop of the diode 6, base driving current is made to flow into the base of the TR5 and current proportional to the DC current amplification factor hFE is branched from the base driving current of the TR20 to the collector current of the TR5. Consequently, the current IB is reduced as shown in Fig. (b) and the TR short current is reduced. |
