278R09 LDO Voltage Regulator 9V, 1A. The 278R09 is a low-dropout voltage regulator suitable for various electronic equipment. It provide constant voltage power source with TO-220 4 lead full mold package. Dropout voltage of 278R09 is below 0.5V in full rated current(2A). This regulator has various function such as peak current protection, thermal shut down, overvoltage protection and output disable function.