Temperature coefficient of voltage regulator diode

As is well known, the voltage regulator diode must be connected in series with a current limiting resistor during use, otherwise it will be burned out. The maximum operating current of a voltage regulator diode (the maximum operating current refers to the maximum current allowed to pass through the voltage regulator diode during operation) is limited by the maximum dissipated power of the voltage regulator diode (the power at which the heat emitted from the diode will damage the diode when the current increases to the maximum operating current).

If the temperature of the voltage regulator diode changes, its stable voltage will also undergo slight changes. The relative change in voltage at both ends of the diode caused by a temperature change of 1 ℃ is the temperature coefficient. Generally speaking, a voltage stabilization value below 6V belongs to Zener breakdown, and the temperature coefficient is negative; A voltage higher than 6V belongs to avalanche breakdown, and the temperature coefficient is positive. When the temperature increases, the depletion layer decreases. In the depletion layer, the valence electrons of atoms rise to higher energy, and a smaller electric field strength can excite the valence electrons from the atoms to produce Zener breakdown. Therefore, its temperature coefficient is negative. Avalanche breakdown occurs when the depletion layer is wide and the electric field strength is low. As the temperature increases, the vibration amplitude of lattice atoms increases, hindering the movement of charge carriers. In this case, only by increasing the reverse voltage can avalanche breakdown occur, so the voltage temperature coefficient of avalanche breakdown is positive. That's why the voltage regulator with a voltage of 15V gradually increases with temperature, while the voltage regulator with a voltage of 5V gradually decreases with temperature.

In situations where high power requirements are needed, two voltage regulators with opposite temperature coefficients can be connected in series as compensation.