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LED Displays - Common Anode or Common Cathode?

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gres

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We try to answer for question which of those system is better.
Firstly let’s try to explain. Common cathode is a LED diode that emitting multisegment light, by a single positive voltage. Each of individual segment consist separate cathode connections. Common Cathode is opposite – powered by negative, separated from anode connections.
Because both of LED drivers can work with source current and sink current choice between depends of what you want to drive by this LED matrix. Also almost all chips can work with both – source and sink current.
Althought that most modern drivers prefer to work with common anode.
Becouse of better current capacity, it is better to use NMOS drives than PMOS. For example if you have current +12V and driver +5V at the same ground, driver for NMOS gate works with 0V/+5V. PMOS doesn’t work with that!
Please remember that if you put in series a single resistor, you must put LED in reverse bias.
With +5V at any LED segment, there will be 220ohm at resistor. Rest or LED segments are off at this time, and are in reverse bias that reduce life of segment. So better option is to create much smaller reverse bias that longer the life of each segment.
Useful information is that NPN is more efficient with common cathode, while PNP is better for common anodes
 

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