7 Segment Display Common Cathode Circuit

A common cathode display is one where the cathode junctions of the LEDs join and connect to the 0 V rail such as ground. Since connection to the anode end controls the individual LEDs, for it to light, a logic 1 state (5 V for TTL circuits) is usually required.

Beginners and hobbyists prefer the common cathode display because logic 1 state is required to light the LED segment.

Common Cathode Circuit

In this circuit, we can see that the diodes join at the cathode end.

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