The ULN2003 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 ULx2004A device is below that of the ULN2003A 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
ULN2003 Pin Configuration and Functions :