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Advantages of schottky diode

Printed From: PCB Libraries Forum
Category: Training / Events
Forum Name: PCB Design Basics
Forum Description:
URL: http://www.PCBLibraries.com/forum/forum_posts.asp?TID=2434
Printed Date: 15 Jun 2019 at 3:31pm


Topic: Advantages of schottky diode
Posted By: vishal4321
Subject: Advantages of schottky diode
Date Posted: 08 Feb 2019 at 2:52am
What are the advantages of schottky diode?



Replies:
Posted By: Tom H
Date Posted: 08 Feb 2019 at 8:27am
The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action.

When sufficient forward voltage is applied, a current flows in the forward direction. A silicon diode has a typical forward voltage of 600–700mV, while the Schottky's forward voltage is 150–450mV. This lower forward voltage requirement allows higher switching speeds and better system efficiency.

A metal-semiconductor junction is formed between a metal and a semiconductor, creating a Schottky barrier (instead of a semiconductor-semiconductor junction as in conventional diodes). Typical metals used are molybdenum, platinum, chromium or tungsten, and certain silicides (e.g., palladium silicide and platinum silicide), whereas the semiconductor would typically be n-type silicon. The metal side acts as the anode, and n-type semiconductor acts as the cathode of the diode; meaning conventional current  can flow from the metal side to the semiconductor side, but not in the opposite direction. This Schottky barrier results in both very fast switching and low forward voltage drop.

The most important difference between the p-n diode and the Schottky diode is the reverse recovery time (trr), when the diode switches from the conducting to the non-conducting state. In a p–n diode, the reverse recovery time can be in the order of several microseconds to less than 100ns for fast diodes. Schottky diodes do not have a recovery time, as there is nothing to recover from (i.e., there is no charge carrier depletion region at the junction). The switching time is ~100ps (pico-seconds) for the small-signal diodes, and up to tens of nanoseconds for special high-capacity power diodes. With p–n-junction switching, there is also a reverse recovery current, which in high-power semiconductors brings increased EMI noise. With Schottky diodes, switching is essentially "instantaneous" with only a slight capacitive loading, which is much less of a concern.


This "instantaneous" switching is not always the case. In higher voltage Schottky devices, in particular, the guard ring structure needed to control breakdown field geometry creates a parasitic p-n diode with the usual recovery time attributes. As long as this guard ring diode is not forward biased, it adds only capacitance. If the Schottky junction is driven hard enough however, the forward voltage eventually will bias both diodes forward and actual trr will be greatly impacted.



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Posted By: vishal4321
Date Posted: 08 Feb 2019 at 10:06pm
Thank you for this guidance..This will be useful for my https://crbtech.in/online-electrical-design-training-course" rel="nofollow - online electrical course studies



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