In summary, a Zener diode features a reverse voltage breakdown characteristic which can be used not only for constant voltage and limiter circuits, but also for circuit protection from surges and overvoltages. A Zener diode prevents surge energy that exceeds the clamp voltage and maintains the surge noise at a level which will damage the circuit. The amount of energy varies depending on the type of surge, therefore the appropriate surge protection diode must be selected for the application. A Zener diode for general-purpose or ESD use is best suited for a noise with small surge energy such as an electrostatic surge. For a transient or instantaneous over- or reverse voltage, a 200 mW Zener diode is sufficient since such a voltage typically exists for a short time and has a low electric energy. Because of the high electric energy, a middle-class 1 W or 2W Zener diode is required for a steady overvoltage. Finally, for a steady reverse voltage, a middle-class Zener diode of 1 W or 2W is also required, due to the extremely high electric energy. Panasonic’s New DZ24 and DZ2W series of Zener diodes features clip type surface mount Zener diodes and offers high power dissipation with wide thermal design margins. These series provide significantly smaller surface mount packages and are capable of 1 W and 2 W.