| 摘要 |
A switching circuit includes a speed-up diode or transistor (Q3A; Q13A) connected in diode-like fashion between a collector load resistor (12; 24) of a switching transistor means (Q5/Q9: Q15/Q20) and a supply voltage terminal (41) for increasing the switching speed. The diode provides a turn-on delay, permitting the switching transistor to more rapidly discharge a parasitic collector capacitor (CA). The diode also provides a turn-off delay to more rapidly charge the parasitic capacitor (CA) when the switching transistor means switches to a nonconductive state. Another load resistor (10) may be connected in series between the collector of the speed-up transistor (Q3A) and the supply voltage terminal (41) to develop the output voltage of the circuit. In this case, the diode-connected transistor (Q3A) serves to buffer the switching transistor means (Q5/Q9) from parasitic capacitances of the output circuits and thereby further increase the switching speed. The switching circuit can be incorporated with a flip-flop circuit to increase its switching speed, which is of importance when the flip-flop is used for instance as a frequency divider in a phase locked loop tuning circuit e.g., for a radio or television receiver. <IMAGE> |
