| 摘要 |
PURPOSE:To reduce noise generated in synchronism with the LED flickering by the secondary radiation of the square wave controlling the power supply voltage fluctuation due to the rapid current change in the LED and the LED flickering when the LED is turned on and off in the battery-driving portable radio device and the reduced voltage display is performed and to enable voice transmission without the sense of incompatibility when the LED is turned on and off. CONSTITUTION:A circuit 1 which controls the LED mode and a transistor 4 which accepts the output of the control circuit 1 drives a LED 2. A capacitor 5 is inserted between the base of the transistor 4 and the power supply. Thus, a base resistance 6 and a time constant circuit are constructed to eliminate the rapid corrector current change at the time of turning on and off the transistor 4. Capacitors 7 and 8 with low impedance are used fully near the transmission frequency so as to reduce the secondary radiation of the LED 2. |
