The ULN2003A devices have a 10.5-kΩ series base resistor to allow operation directly from CMOS devices that use supply voltages of 6 V to 15 V. The required input current of the ULN2003A device is below that of the ULN2004A devices, and the required voltage is less than that required by the ULN2002A device.
The ULN2002A device is designed specifically for use with 14-V to 25-V PMOS devices. Each input of this device has a Zener diode and resistor in series to control the input current to a safe limit. The ULx2003A devices have a 2.7-kΩ series base resistor for each Darlington pair for operation directly with TTL or 5-V CMOS devices.
UNL2003 Pin Configuration and Functions :
Download UNL2003A IC datasheet pdf.