ULN2003A - Darlington Transistor Drivers Arrays

These are high-voltage, high-current Darlington transistor arrays. Each consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diodes for switching inductive loads.

The collector-current rating of a single Darlington pair is 500 mA. The Darlington pairs can be paralleled for higher current capability. Applications include relay drivers, hammer drivers, lamp drivers, display drivers (LED and gas discharge), line drivers, and logic buffers.

ULN2003A - Darlington Transistor Drivers Arrays

The ULx2004A 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. 

Using the ULN2003A

delabs Notes

The output logic of your embedded system port bit (one pin) goes high  it can drive a drive a ULN2003A. - The output of this is open collector and can operate relays or lamps.

It is not a good idea to heat the ULN2003A chip too much. Keep the return paths of these to a separate but linked ground as they carry more current.

If you are running short of ports in the Embedded System. Latch the Output by using 74HCT373. There may be logic level comparability issues, check your Embedded System Supply. There may be ground loop problems if you design the PCB without understanding current paths.

Use ULN to drive PNP Transistor and things like a Motor, Solenoid, Large Relay or Lamps; when current needs become more like 1 amp.

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