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What is a diode?

Schottky Barrier Diodes (SBD): Structure and Features

Structure Symbol Applications・Characteristics
Figure - SBD Structure Figure -SBD Symbol
  • Used for secondary power supply rectification
  • Low VF(low loss),large IR
  • Fast switching speed

Unlike conventional diodes that provide diode characteristics through a PN (semiconductor-semiconductor) junction, Schottky barrier diodes utilize a Schottky barrier consisting of a metal-semiconductor junction.This results in much lower VF characteristics (forward voltage drop) compared with a PN junction diodes, enabling faster switching speeds. However, one drawback is larger leakage current (IR), making countermeasures necessary to prevent thermal runaway.

Figure - Schottky barrier diodes feature low VF but large IR

SBDs, which are often used for secondary power supply rectification, feature characteristics that can vary greatly depending on the type of metal used. ROHM offers a broad lineup of industry-leading SBDs that utilize a variety of different metals.

  • RB**1 series low VF type
  • RB**0 series low IR type
  • ROHM offers the RB**8 series of ultra-low-IR diodes for automotive applications
Key Points
  • Low VF and IR types can be achieved by simply changing the type of metal.
Thermal Runaway

Schottky barrier diodes are susceptible to excessive heat generation during large current flow. As a result, the combination of high heat with increasing IR (leakage current) can cause both the case and ambient temperature to rise. Consequently, implementing incorrect thermal design may result in the amount of heat generated to exceed the amount dissipated, which can lead to increasing heat generation and leakage current and eventually result in damage. This phenomenon is referred to as thermal runaway.

Figure - Heat generation > Heat dissipation→Stable IR/Heat generation <Heat dissipation→Thermal Runaway
Key Points
  • High ambient temperatures can cause thermal runaway
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