EducationWhat is Switching Diode? - Characteristic, Symbol, Definition

What is Switching Diode? – Characteristic, Symbol, Definition

Category articles

Switching Diode (also called a Pulse Diode, Schottky Diode) – semiconductor diode used in pulse (discrete) systems. It mainly operates in switching configurations, which generate a pulse of only one sign (+), forward-bias. Depending on the application, switching diode can also operate as a simple rectifier diode,transient-voltage-suppressor or detection diode). It is characterized by a very fast operation rate (measured in nanoseconds, whereas for higher voltages – microseconds).

Most sought after parameters of switching diode, operating as a switching device are as follows:

  • Very low resistance in the forward bias and very high resistance in the reverse bias,
  • Switching process of the diode should occur as soon as possible (the least possible delay and no distortion of pulses).
switching diode symbol
Fig. 1 switching diode symbol

The Switching Diode has an extremely low junction capacitance, which leads to a really low switching time. Such properties indicate a contrast using the blade diode, that has properties that are similar. Nonetheless, the Switching Diode is a lot less undependable (also automatically – shock resistant), characterized by a more compact number of parameter values, substantially lower inverse current, lower resistance in the conduction management, but greater parasitic capacitance. At a coating diode, a comparatively large charge accumulates from the p-n junction through conduction, which simulates diodes with these kinds of properties, amongst others, from suitability for jobs where, as an instance, that they need to manage high frequencies. The Switching Diode has rather low inertia just since the fee that collects at the metal-semiconductor junction is little – making it really well suited to switching and very significant frequency ranges. This is only one of the most essential properties which make Fast Switching Diodes used as elements of pulse chargers (like the ones used now to power bulbs, among other objects ) or mixers (electronic circuits which need to create a third signal out of 2 varying signs, using a frequency that’s a mix of the signals in the input signal ).

Switching Diode Includes a coating of metal and also a coating of semiconductor, that’s often silicon. Its properties make it ideal for all applications in electronic equipment – as A component which protects sensitive digital circuits as well as a rectifier utilized For signals whose frequency is extremely large. It performs better at this Application compared to standard silicon diode – it is different mostly by reduced Voltage drop and even higher frequency indicates it may manage successfully. Its working characteristics have caused it to be frequently called a hot tub Diode or even a barrier diode. The Minimal conduction voltage begins around 150 mV as much as Roughly 500 mV, using the lowest importance of silicon diodes being at 600 mV. The so-called barrier junction (frequently Known as a Barrier Switching Diode) Described before is formed by linking a semiconductor into some metal. The Semiconductor is generally silicon, although the alloy is most frequently chosen from Platinum, tungsten, molybdenum, or chromium. The Selection of the collection of substances That will function as the anode (kind of alloy ) and the cathode (kind of Semiconductor) decides what worth of this conduction voltage that the Switching Diode will get.

Switching Diode Characteristic

Characteristic of switching diode is shown below on Fig. 2.

switching diode characteristic
Fig. 2 switching diode characteristic


  • Fast switching diodes – they are manufactured with application of semiconductor materials with a wider band gap (e.g. Gallium Arsenide (GaAs): trr < 0,1ns). Schottky diodes have significantly shorter switching times (small junction capacity Cj values) compared to regular semiconductor diodes (trr of 100ps), which is due to their junction construction”M-S” junction capacity,
  • Low decay time diodes (also called step-recovery diode) – in this kind of diodes, storage of charge has a crucial impact on the diode operating speed. It is used to generate rectangular pulses (tf decay time must be very small).

Limiting parameters

  • IFmax – maximum constant bias,
  • IFMmax – peak, maximum permissible diode bias,
  • VRmax – maximum constant reverse voltage,
  • VRMmax – maximum peak reverse voltage,
  • Tj – permissible junction temperature.

Static and dynamic parameters

  • VF – forward voltage at a determined IF forward current (the higher the current, the greater the charge is stored on the pn junction diode basis and the defusing process is slower)
  • IR – reverse current at a given VR reversing voltage (the higher the current, the faster the charge that is stored in the junction will be unloaded, diode will switch faster)
  • Capacitance of the diode (at determined reverse voltage and frequency),
  • trr – duration of diode switch (occasionally, instead of trr time, Qrr switching charge that is accumulated in connector is given).

Heat dissipation efficiency

Vacuum residue makes it a really great “opportunity” to have the ability to use the metallic coating into the semiconductor substrate as much as you can. Even the anode becomes the metallic aspect, although the cathode is that the semiconductor. The metal behaves chiefly as a resistive touch for your anode – it’s nothing but a thin coating placed on the silicon. This type of solution shows a sort of disadvantage observable compared to conventional silicon diodes. Elements with this kind of thin wires frequently turn into “weak links” and also make the full diode is not as resistant to flashover. Furthermore, it might be well worth noting the Switching Diode worse copes with all the radiated heat in the system in connection with its tight counterpart using a p-n junction. The main reason for these properties is that the usage of alloy, which can be in direct contact with all the Switching Diode junction.

Regeneration time

A Switching Diode is a semiconductor electronic part whose among the most crucial and distinguishing features differentiating it from a conventional junction diode is that the simple fact that its bulk carriers are electrons. This is since there are several more of these in an N-type semiconductor (from the cathode – typically silicon) than from the anode, because of that they behave as current carriers. The metallic coating is entirely electrically inert. These features combine to create Fast Switching Diode less inert than conventional diodes. The last explanation is the simple fact that there’s no so called cranial area in the junction, which translates into a really brief recovery period. It’s required to transition from some country where the diode conducts into a state once it plays a barrier purpose (by way of instance, protecting the circuit in an insufficient power source, which could damage the mounted sensitive electronics parts when current flows in the opposite direction). The difference between conventional diodes using p-n junctions is important, since in the ideal case the so-called p-n diode will call for a few hundred nanoseconds, and it could even happen to be a few thousand nanoseconds, whereas the Switching Diode may utilize from tenths of components to a max of thousands of nanoseconds for regeneration.

Switching Diode Applications

Short switching times of the Fast Switching Diodes are sought after in many applications. Some of the most typical ones include:

  • Voltage clamping,
  • High speed rectifying and switching circuits,
  • Reverse current and discharge protection,
  • Switched-mode power supplies (as a rectifier).

The Switching Diode’s high efficacy when managing very higher frequency signals which makes it a wonderful choice for a surge protector set before the input signal into a circuit that is sensitive. Very brief regeneration period makes it a really practical component employed in inverters or boost converters. Low voltage and also incredibly brief regeneration period makes the efficacy of the energy source considerably higher – it may reach worth even up to 90 percent efficacy. It’s well worth recalling that this sort of diodes can be utilized for current frequencies not exceeding 100 GHz. Switching Diode is often a sensible alternative to use rather than germanium diodes – particularly whenever the threshold voltage must be as low as you can (that in this instance is all about 0.4 V). The minimal voltage fall makes it an fantastic component for linking redundant power resources – fantastic for inverters, along with other programs. During operation it’s necessary to focus on the temperatures which exist in the circuit, as between 25 and 100 degrees Celsius the significance of their so-called reverse current could increase even double.

Checking the correct operation of the diode

It might occur that a device outfitted with this kind of electronics stops functioning, along with also the Switching Diode is imagined this fault. By way of instance, it might be a power source in the screen or a TV set. In this moment it’s vital to assess whether the part works correctly. But it’s well worth understanding the way to do it properly. Attempting to check a barrier diode in exactly the exact identical manner as a normal diode won’t offer the desired benefits. The purpose is that the exact outcomes of the very exact tests for some forms of diodes are disqualifying to them, and also for many others mean the right operation. Fairly often in electronics of the kind (power supplies for televisions or monitors ) are utilized elements, where more than 1 diode is put, although in the outside seems like one component. Very often you will find two diodes included in one housing, which may be located in the catalogue notice, in which there will be a diagram of the whole component (the so called info sheet file ). The very first action of a individual undertaking this job ought to be a comprehensive analysis of exactly what the analyzed element is if it’s absolutely a Switching Diode, how it’s constructed and just what is your pinout distribution. Then, dependent on knowledge located in reputable sources on the Internet, as an instance, a set of evaluations should be designed to determine the current condition of this diode. With this, you are certainly going to should use a multimeter using an ohmmeter.

Michal Pukala
Electronics and Telecommunications engineer with Electro-energetics Master degree graduation. Lightning designer experienced engineer. Currently working in IT industry.



    • The reverse recovery time trr refers to the time it takes for the switching diode to turn completely OFF from an ON state. Generally, electrons cannot be stopped immediately after operation turns OFF, resulting in some current flow in the reverse direction.The higher this leakage current is, the greater the loss. However, reverse recovery time can be shortened through heavy metal diffusion, material optimization, or by developing FRDs (Fast Recovery Diodes) that suppress ringing after recovery.