What’s inside the ULN2003 Darlington driver chip

Darlington chip

ULN2003 – practical example of «reading» microchip schematic via Evil Mad Scientist

We often receive comments that while out microchip photos are beautiful and interesting, it is completely unclear how integrated circuit implements basic elements and form larger circuit. Of course it is impossible to do a detailed review of an 1’000’000 transistor chip, so we’ve found simpler example: ULN2003 – array ofDarlington transistors.

Despite it’s simplicity this microchip is still widely used and mass manufactured. ULN2003 contains 21 resistors, 14 BJT transistors and 7 diodes. It is used to control relatively high load (up to 50V/0.5A) from microcontroller pin. Canonical use case – to control segments of large 7-segment LED displays.


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