Schottky Diode

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A schottky diode, also known as schottky barrier diode or hot electron diode, has a low forward voltage drop with a very fast switching characteristics. Common forward voltages are from about 0.3V. The common 1N5817 has a forward voltage of ~0.32V at a 0.1A forward current and ~0.45V @ 1.0A and ~0.75V @3.0A respectively.

It is a solid state diode in which the junction is formed by a metal-semiconductor contact. The schottky diode is usually fabricated from lightly doped substrate/N-type material and a metal such as aluminium. A highly doped substrate would give a poor ohmic contact and a high series resistance, thus not practical.
The metal has been evaporated or sputtered onto the semiconductor. The hot carrier diode is a form of schottky diode.

Schottky diodes are characterized by extremely rapid switching capability. The reverse bias capacitance is very low. They are useful at VHF and UHF frequencies because of their high-speed properties. They are used as the switching elements in commutating mixers, harmonic generators and detectors. Especially detectors at very low signal levels,and in other applications requiring diodes.
The schottky diode design has sometimes been used in the manufacture of transistors then to form a schottky transistor.

Some advantages with schottky diodes

Less power loss due to low turn on/forward voltage

A schottky rectifier has a smaller power loss compared to other diode rectifiers (except germanium). Because the turn on voltage is ~ 0.6-0.7 volts in most ordinary diodes, a schottky diode rectifier only has a turn on voltage as low as 0.2 to 0.3 volts. For low voltage applications, a significant power saving can be gained.

Faster switching with faster recovery time.

This will improve efficiency in a switched power supply.

Lower junction capacitance.

Together with faster switching, is why schottky diodes can be better for many RF or other high frequency applications.


Related to the advantages above, some common applications are

Low voltage applications such as for solar cell chargers to protect for reverse charge applied.
RF mixers such as ring mixers and detectors
Reverse current or discharge protection.
Switching power supplies.
Clamp diode to speed up transistor switching.

Common schottky diodes

1n5817, 1n5818, 1n5819 are maybe the most common. Some widely used small signal schottky diodes are 1n5711, 1n6263, 1ss106, 1ss108 or the bat41–43, 45–49 series are widely used in high frequency applications as mixers, detectors and nonlinear elements.

Updated September 22 2015

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