Compensation of temperature coefficient of Zener Diode

Compensation of temperature coefficient of Zener Diode.
The relative change of the voltage at both ends of the Zener diode caused by the temperature change of 1 ℃ is the temperature coefficient of the Zener diode.
As we all know, Zener diodes must be connected in series with current limiting resistors, otherwise they will be burnt out. The maximum working current of the Zener diode (the maximum working current is the maximum current allowed to pass through when the Zener is working) is limited by the maximum dissipated power of the Zener (when the current increases to the maximum working current, the heat emitted from the diodee will damage the diodee).
If the temperature of the voltage stabilizer changes, its stable voltage will also change slightly. Generally speaking, the steady voltage lower than 6V belongs to Zener breakdown and the temperature coefficient is negative, while the one higher than 6V belongs to avalanche breakdown and the temperature coefficient is positive.
When the temperature increases, the depletion layer decreases, and in the depletion layer, the valence electrons of the atoms rise to a higher energy, and the smaller electric field intensity can excite the valence electrons from the atoms to produce Zener breakdown, so its temperature coefficient is negative. Avalanche breakdown occurs when the depletion layer is wide and the electric field strength is low, and the increase of temperature increases the vibration amplitude of lattice atoms, which hinders the movement of carriers. In this case, the avalanche breakdown can occur only by increasing the reverse voltage, so the voltage temperature coefficient of the avalanche breakdown is positive. This is why the voltage stabilizing value of the voltage stabilizing diodee with a steady voltage value of 15V increases gradually with the temperature, while the voltage stabilizing value of the voltage stabilizing diodee with a steady voltage value of 5V decreases with the temperature.
In the case of high demand for power supply, two voltage stabilizer diodees with opposite temperature coefficient can be connected in series as compensation. Due to mutual compensation, the temperature coefficient is greatly reduced, and the temperature coefficient can reach 0.0005% / ℃.