Commonanode

Common anode is a configuration for multi-LED assemblies in which the anodes of all diodes are connected together to a common positive supply. This arrangement is frequently used in seven-segment displays, LED matrices, and RGB LED modules. In a common anode display, the shared node is typically tied to a positive voltage, such as +5V or +3.3V.

Operation in a common anode circuit involves sinking current through the individual cathodes. To light a specific LED, the corresponding cathode is driven low (toward ground) through a current-limiting resistor. To turn the LED off, the cathode is driven high or left floating, stopping the current flow. The required current-limiting resistor can be placed on each LED branch or on the common supply line in some configurations, but per-branch resistors are common to control individual LED currents.

Common anode is the opposite of the common cathode configuration, in which the LEDs share a common ground and are lit by driving their anodes high. The choice between common anode and common cathode affects how drivers and microcontroller outputs are wired; sinking current (pulling cathodes low) is often simpler in practice for many digital drivers.

Considerations when using common anode devices include ensuring that the supply voltage and LED forward voltages are compatible, providing adequate current limiting, and matching drivers to sink capability. These displays are widely used in digital readouts and indicator panels, and the module type is indicated by its datasheet as common anode or common cathode.