Asia-Pacific
English
简体中文
繁體中文
한국어
日本語
Americas
English
Europe (EMEA)
English



Part Number Search

Cross Reference Search

About information presented in this cross reference

The information presented in this cross reference is based on TOSHIBA's selection criteria and should be treated as a suggestion only. Please carefully review the latest versions of all relevant information on the TOSHIBA products, including without limitation data sheets and validate all operating parameters of the TOSHIBA products to ensure that the suggested TOSHIBA products are truly compatible with your design and application.
Please note that this cross reference is based on TOSHIBA's estimate of compatibility with other manufacturers' products, based on other manufacturers' published data, at the time the data was collected.
TOSHIBA is not responsible for any incorrect or incomplete information. Information is subject to change at any time without notice.

Keyword Search

Parametric Search

Stock Check & Purchase

1-1 Reverse breakdown voltage

Figure 1.3 Zener breakdown
Figure 1.3 Zener breakdown

The reverse breakdown voltage is determined by Zener breakdown or avalanche breakdown.

Zener breakdown

When a pn junction is reverse-biased, a depletion layer extends across the pn junction. An electric field causes a gap between the valence band of the p-type region and the conduction band of the n-type region to decrease inside the depletion layer. As a result, electrons tunnel from the valence band of the p-type region to the conduction band of the n-type region because of quantum tunneling. Zener breakdown is a phenomenon in which the tunneling of electrons across the depletion region causes a sudden increase in reverse current. Figure 1.3 illustrates Zener breakdown.

Avalanche breakdown

When a pn junction is reverse-biased, a small quantity of electrons passes through the pn junction. These electrons are accelerated in the depletion layer by an electric field, acquiring large kinetic energy. The accelerated electrons collide with the atoms in a crystal lattice, ionizing them and creating electron holes. The electrons of these atoms are excited to the conduction band and knocked out, becoming free electrons. The free electrons are also accelerated and collide with other atoms, creating more electron-hole pairs and leading to further knocking-out processes. This phenomenon is called avalanche breakdown.

Comparison of avalanche breakdown and Zener breakdown

Since diodes with high breakdown voltage are lightly doped, they form a wide depletion layer (forbidden band). Conversely, since diodes with low breakdown voltage are heavily doped, they form a thin depletion layer (forbidden band). When a diode has a wide depletion layer, electron tunneling (Zener breakdown) is less likely to occur, causing avalanche breakdown to become more predominant. In the case of a heavily doped diode with a thin depletion layer, Zener breakdown is more like to occur. As temperature increases, the width of the forbidden band (Eg) decreases, contributing to the Zener effect. In addition, as temperature increases, the lattice vibration of a semiconductor increases, causing its carrier mobility to decrease. As a result, avalanche breakdown becomes less likely to occur. Zener breakdown voltage decreases with temperature whereas avalanche breakdown voltage increases with temperature. Generally, Zener breakdown is predominant below roughly 6 V whereas avalanche breakdown is predominant above roughly 6 V. It should be noted that even diodes of the same product series exhibit different temperature characteristics.

Figure 1.4 Avalanche breakdown
Figure 1.4 Avalanche breakdown

1 What is a TVS diode (ESD protection diode)?

1 What is a TVS diode (ESD protection diode)?
1-2 Using different types of protection diodes (ESD protection diodes and Zener diodes for overvoltage protection)
1-3 Differences between protection diodes (ESD protection diodes and surge protection Zener diodes) and diodes for constant-voltage regulation

Related information