ICs such as the BCR401U provide high-quality control of LEDs for applications that require something better than the typical series-resistor arrangement.

We all know that you can drive an LED with nothing more than a voltage source and a series resistor. But this is not the optimal approach. I won’t go into all the details because we already have an article that covers this topic. Here’s the abbreviated version:

Current vs. Voltage

The critical parameter when driving an LED is forward current, not forward voltage or applied voltage. The relationship between forward current and brightness is approximately linear, whereas the relationship between forward voltage and brightness is exponential. This means that small changes in forward voltage correspond to large changes in brightness; it also means that precise control of LED brightness is more easily achieved by adjusting the current.

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