ULN2803A chip is an integrated circuit with 8-way high-drive relay drive circuit, which can be used to convert low-voltage control power to high-voltage output signal.
At its core is a circuit consisting of eight Darlington driver chips, each with a 500mA current drive capability and a 500V trip switch voltage.
It also has a variety of safety protection measures to avoid thermal damage and short circuit phenomenon, making the circuit use more reliable.