Working principle and application circuit of Zener diode

Zener diode, also known as germanium diode, is a commonly used type of diode. It was invented by German physicist Zener in the early 20th century, hence its name. Zener diode is a semiconductor device made of germanium material, with two electrodes, namely positive electrode (anode) and negative electrode (cathode). Essentially, a Zener diode is a PN junction diode that has the characteristics of forward conduction and reverse cutoff.

working principle:

1. Forward bias (conducting state): When sufficient voltage is applied to the forward connection of the Zener diode, electrons flow from the N-type region to the P-type region, while holes flow from the P-type region to the N-type region, causing the PN junction region to conduct and forming current flow. In this case, the Zener diode exhibits a low resistance state, and the voltage drop across its terminals is relatively small.

2. Reverse bias (cut-off state): When a reverse voltage is applied to a Zener diode, an electric field is formed due to the presence of the PN junction, completely isolating holes and electrons, preventing current from passing through the diode. At this point, the diode is in a high resistance state, known as the reverse cut-off state.

Application circuit:

1. Rectifiers: Zener diodes can be used as diodes in half wave rectification or full wave rectification circuits to convert AC signals into DC signals.

2. Voltage regulator: Zener diodes can be combined with other components to form a voltage regulator circuit for stabilizing voltage output.

3. Switching circuit: Zener diodes can be used as switches to control the operation of the circuit by switching between conductive and non-conductive states.

4. Detector: Zener diodes can be used as detectors in radio receivers to convert RF signals into audio signals.

It should be noted that although Zener diodes have been replaced by more advanced silicon diodes and other semiconductor devices, they are still used in certain low-frequency applications.