This whitepaper will first return to basics to understand the operating principles of LEDs and how they need to be correctly biased to achieve the optimum light output performance specified by the manufacturers. This paper will also look at the electrical, optical, and thermal characteristics of LEDs to appreciate why driving several LEDs in series can be more efficient than overdriving single LEDs, and why keeping temperatures in check is not just key to maximizing output but also to maintaining the desired color tone and ensuring reliability and long life.