View lt1123 datasheet:

LT1123 Low Dropout Regulator Driver DESCRIPTIO FEATURES Extremely Low Dropout The LT1123 is a 3-pin bipolar device designed to be used Low Cost in conjunction with a discrete PNP power transistor to Fixed 5V Output, Trimmed to ±1% form an inexpensive low dropout regulator. The LT1123 700µA Quiescent Current consists of a trimmed bandgap reference, error amplifier, 3-Pin TO-92 Package and a driver circuit capable of sinking up to 125mA from 1mV Line Regulation the base of the external PNP pass transistor. The LT1123 5mV Load Regulation is designed to provide a fixed output voltage of 5V. Thermal Limit The drive pin of the device can pull down to 2V at 125mA 4A Output Current Guaranteed (1.4V at 10mA). This allows a resistor to be used to reduce the base drive available to th