Product description
ULN2803 is a transistor driver circuit (Darlington array) with eight channels of NPN transistors in a single IC, intended for driving loads that require higher rated current and voltage than typical GPIO outputs can provide.
Function:
ULN2803 accepts logic levels of 3.3 V or 5 V from a microcontroller and amplifies them to drive larger loads than the microcontroller’s output pins can handle. The amplification is achieved through internal Darlington-connected transistor stages. Each channel can be connected to an external load and provides a collector-to-emitter current path that is activated when the input is high.
Typical applications:
ULN2803 is used when there is a need to control devices with higher rated current and/or rated voltage than a microcontroller can handle directly.
- Relays
- Motors – control of DC motors or stepper motor windings (via external current limiting or an H-bridge)
- Lamps and LED matrices
- Solenoids and valves
- TTL/CMOS interfaces to mechanical components – buffering of control signals for robust operation
Specifications:
- Number of channels: 8
- Input level: compatible with TTL/CMOS logic (typically 3.3–5 V)
- Rated current (max): up to 500 mA per channel
- Rated voltage (max): up to 50 V
- Internal diodes: built-in flyback diodes for inductive loads such as relay coils and solenoids, protecting against voltage spikes during switch-off
