ULN2803 Darlington Transistor Array

Description

ULN2803?is?a high-voltage and high-current Darlington transistor array and is mainly used as a relay driver with an ability?to handle 8?relays?at a time. It comes with a collector-emitter voltage around 50 V and input voltage residing at 30 V. Before we move further, we must know what is?Darlington transistor? It is commonly known as?Darlington pair which is nothing but a combination of two?bipolar transistors?featuring a compound?design and is connected?back to back?where current amplified by the first transistor is again amplified by the second one. This shape delivers a much higher?current gain as compared to each transistor taken separately. It works on the simple amplification principle happening in the regular transistor where a small base is used to make the pair switch for higher switching currents. This?Darlington transistor mainly operates at 5V? and is based on TTL (Transistor-Transistor Logic) and CMOS (Complementary Metal Oxide Semi-Conductor). The?NPN transistors?forming arrays are useful for both: interfacing between low logic level digital circuitry and achieving the higher current/voltage requirements in a wide range of applications including printer hammers, lamps, relays, consumer and industrial applications. The device shows open?collector outputs and freewheeling clamp diodes that turn out to be very handy for transient suppression. ULN2803 Pinout Following figure shows the pinout of ULN2803. It comes with 8 input pins and 8 output pins. Pin Configuration