Today, I'm going to give you a thorough overview of Schottky Diode. This blog is the continuous blog of the series of Diodes so if you wish to read about any other diodes or basic's of diode then you may visit our website. In this blog, we will be discussing the Definition, Symbol, Construction, Schottky Diode IV-Characteristics, Advantages of the Schottky diode, How to choose a perfect Schottky diode, Functions of Schottky Diode, Applications, Schottky Diode's model number with their application and so on.
Schottky Diode
The Schottky Diode is a type of semiconductor diode that, like any other junction diode, may be utilized in a variety of wave shaping, switching, and rectification applications as well as TTL and CMOS logic gates. The key benefit is that a Schottky Diode's forward voltage drop is much lower than a regular silicon PN-junction diode's 0.7 volts.
Due to their low power and high switching rates, Schottky diodes are used in a wide range of applications. TTL Schottky logic gates are identified by the letters LS appearing somewhere in their logic gate circuit code, e.g. 74LS00.
Schottky Diode Construction and Symbol
Unlike a typical PN-junction diode, which is made up of a P-type and an N-type semiconductor, Schottky Diodes are made up of a metal electrode attached to an N-type semiconductor. Schottky diodes have no depletion layer and are classified as unipolar devices.
The schematic and symbol for a Schottky diode are shown above.
There is no p-type semiconductor material and hence no minority carriers (holes) so when reverse biased, the diode's conduction ceases extremely rapidly and turns to block the current flow. As a result, a Schottky diode responds very quickly to changes in bias, displaying the properties of a rectifying diode of Fast recovery.
Schottky Diode IV-Characteristics
"Silicide," highly conductive silicon and metal, is the most common contact metal being used in Schottky diode manufacturing. When conducting, this silicide metal-silicon contact has a low ohmic resistance, enabling more current to flow and resulting in a decreased forward voltage drop of about 0.4V. Forward voltage drop is generally between 0.3 and 0.5 volts, depending on the metal composition.
The Schottky diode's decreased power loss makes it an ideal choice for low-voltage, high-current applications like solar photovoltaic panels, where the forward voltage (VF) drop across a normal pn-junction diode would cause excessive heating.
However, the reverse leakage current (IR) of a Schottky diode is often substantially higher than that of a pn-junction diode.
Schottky diodes are also somewhat more costly than normal pn-junction silicon diodes with comparable voltage and current requirements since they are constructed with a metal-to-semiconductor junction. For example, the 1N58xx
Advantages of Schottky diode
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Low junction capacitance
Capacitance is characterized as the capacity to store an electric charge. The depletion region or stored charges in a Schottky diode are minimal. As a result, the capacitance of a Schottky diode is extremely low.
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Fast reverse recovery time
The amount of time it takes for a diode to switch from ON state to OFF state is called reverse recovery time.
In order to switch from ON (conducting) state to OFF (non-conducting) state, the stored charges in the depletion region must be first discharged or removed before the diode switch to OFF (non-conducting) state.
However, in the Schottky diode, the depletion region is negligible. So the Schottky diode will immediately switch from ON to OFF state.
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High current density
In the Schottky diode, we know that the depletion area is quite small. As a result, a low voltage is sufficient to generate a big current.
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Low forward voltage drop or low turn-on voltage
The Schottky diode has a turn-on voltage of 0.2 to 0.3 volts. As a result, a low voltage is all that is required to generate an electric current in a Schottky diode.
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High-efficiency
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Schottky diodes operate at high frequencies.
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Schottky diode produces less unwanted noise than P-N junction diode.
Schottky Diode Parameters
A list of parameters to consider when selecting a Schottky diode for your next electronics project may be found below:
|
Parameters |
Description |
|
Forward Voltage Drop |
The forward voltage drop for a given current may be found in any component specification. Most Schottky diodes have a typical turn-on voltage of roughly 0.2V. |
|
Reverse Leakage Current |
The reverse leakage current of a Schottky diode increases dramatically as the temperature of the diode rises. This is a critical element to keep in mind if you want to keep your device's integrity. |
|
Reverse Recovery Time |
The amount of charge that flows during the transition from an on to an off state is described by this parameter. The time is commonly expressed in nanoseconds or picoseconds. |
|
Reverse Breakdown |
To figure out when the diode will allow current to flow in reverse, look for factors like Peak Reverse Voltage or Maximum Blocking DC Voltage. |
|
Capacitance |
A Schottky diode's junction area is tiny, and capacitance is commonly measured in picofarads. |
|
Working Temperature |
The junction temperature of a basic Schottky diode must be kept between 125 and 175 degrees Celsius. When working on heat distribution for your product, keep this number in mind. |
Functions of Schottky Diode
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Rectification
Due to Schottky diodes' unidirectional conductivity, alternating currents in alternating directions can be transformed to pulsed direct currents in a single direction.
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Switch
Under the action of forwarding voltage, Schottky diodes resistance is extremely low, and they are in an on state, which is equivalent to the switch. Under the action of reversing voltage, their resistance is very big, and they are in an off state, which is comparable to an off switch. Various logic circuits may be constructed utilizing the switching properties of Schottky diodes. The Schottky diode will be able to regulate the current on or off in the circuit as a result of this property, making it a perfect electronic switch.
- Amplitude limiting
The purpose of a limiting Schottky diode is to keep the signal's amplitude within a certain range. Because high-frequency pulse circuits, high-frequency carrier circuits, high-frequency signal amplification circuits, and high-frequency modulation circuits frequently need limiting, limiting Schottky diodes have steep Vl characteristics to provide effective switching performance.
- Freewheeling
In an inductor or any coil device, the electromotive force at both ends does not disappear instantly when the inductor is turned off. A Schottky diode is used to release the leftover electromotive force at this point. This ensures the safety of the circuit's other components. To prevent reverse breakdown, freewheeling diodes are employed in inductor coils, relays, and thyristor circuits.
The technique of connecting is depicted in the diagram above. The Schottky diode's negative pole is linked to the coil's positive pole, and the Schottky diode's positive pole is connected to the coil's negative pole.
Applications
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Schottky diode applied to dual power
Currently, the real-time clock (RTC) is mostly employed in electronic design with the primary controller. To prevent the time information from being lost once the system is turned off, the RTC requires an additional button battery. In order to increase the battery life, the primary system is often energized once the system is started. As a result, two power sources are frequently required for RTCS, and diodes can offer power isolation owing to their one directional conductivity. The maximum forward voltage drop (at a forward current of 0.1ma) of the small-signal Schottky diode BAT54C is just 0.24v, and the RTC current consumption is likewise a level. It may also fully fulfil the requirements by adding the Schottky diode isolated power supply.
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Schottky diodes used as AND gate
As shown in the figure below, Schottky diodes form an n-input AND gate. As long as there is a signal output logic 0 in A1 ~ An, Output is logic 0. Only all signals in A1 - An output logic 1 and Output can be logic 1. That is, the AND of the signals A1-An is realized. Because in the digital circuit, the signal input stage of the chip is basically high-impedance, the overall current of the AND circuit composed of Schottky diodes is a level. The voltage drop of the Schottky diode is extremely small, and the ping can still meet the design requirements.
- Schottky diodes used as OR gate
An n-input OR gate is formed by Schottky diodes, as shown in the diagram below. The output will be logic 1 as long as there is a signal output logic 1 in A1 - An. Only all signals in A1 have a logic 0 output, and only logic 0 outputs are allowed. That is, the A1 - An signals' phase OR is accomplished.
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Voltage clamping
While standard silicon diodes have a forward voltage drop of about 0.7 V, Schottky diodes' voltage drop at forwarding biases of around 3 mA is in the range of 0.15 V to 0.46 V (see the 1N5817 and 1N5711), which makes them useful in voltage clamping applications and prevention of transistor saturation. This is due to the higher current density in the Schottky diode.
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Discharge protection
Because of a Schottky diode's low forward voltage drop, less energy is wasted as heat, making them the most efficient choice for applications sensitive to efficiency. For instance, they are used in stand-alone ("off-grid") photovoltaic (PV) systems to prevent batteries from discharging through the solar panels at night, called "blocking diodes".
Schottky diode's Model number with their application
Commonly encountered Schottky diodes include the 1N58xx series rectifiers, such as the 1N581x (1 A) and 1N582x (3 A) through-hole parts, and the SS1x (1 A) and SS3x (3 A) surface-mount parts. Schottky rectifiers are available in numerous surface-mount package styles.
Small-signal Schottky diodes such as the 1N5711,1N6263,1SS106, 1SS108, and the BAT41–43, 45–49 series are widely used in high-frequency applications as detectors, mixers and nonlinear elements, and have superseded germanium diodes. They are also suitable for electrostatic discharge (ESD) protection of sensitive devices such as III-V-semiconductor devices, laser diodes and, to a lesser extent, exposed lines of CMOS circuitry.
Schottky metal-semiconductor junctions are featured in the successors to the 7400 TTL family of logic devices, the 74S, 74LS and 74ALS series, where they are employed as Baker clamps in parallel with the collector-base junctions of the bipolar transistors to prevent their saturation, thereby greatly reducing their turn-off delays.
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