Diode equivalent chart


  • How Schottky Diodes Work
  • Difference between Diode and Zener Diode
  • Types of Diodes | Small Signal, LED, Schottky, Zener
  • These diodes are manufactured using semiconductor materials like Silicon, Germanium and Gallium Arsenide. The two terminals of the diode are known as Anode and Cathode. Based on the potential difference between these two terminals, the operation of diode can be classified in two ways: If anode has higher potential than cathode, then the diode is said to be in Forward Bias and it allows current to flow.

    Different types of diodes have different voltage requirements. For Silicon Diodes, the forward voltage is 0. Usually, in Silicon Diodes, the dark band on one end of the diode indicates the Cathode terminal and the other terminal is anode.

    One of the main application of Diodes is Rectification i. Since diodes allow current to flow only in one direction and blocks current flow in the other direction, diodes are used in reverse polarity protector and transient protector applications.

    There are many Different Types of diodes and some of them are listed below. Different Types of Diodes Let us now briefly see about few common types of diodes. Small Signal Diode It is a small device with disproportional characteristics whose applications are mainly involved at high frequency and very low current applications such as radios and televisions etc.

    To protect the diode from contamination it is enveloped with a glass so it is also named as Glass Passivated Diode. One of the popular diodes of this type is the 1N Appearance wise, signal diodes are very small when compared with power diodes. To indicate the cathode terminal, one edge is marked with black or red color.

    For applications at high frequencies, the performance of the small signal diode is very effective. With respect to the other functionalities, the signal diodes usually have a small current carrying capability and power dissipation.

    Usually, these are in the range of mA and mW respectively. The Small Signal Diode can be made of either Silicon or Germanium type semiconductor material, but the characteristics of the diode varies depending up on the doping material. Small Signal Diodes are used in general purpose diode applications, high speed switching, parametric amplifiers and many other applications. Reverse Current IR — The current very small value that flows when it is reverse biased.

    Thus, they are usually used in rectification i. The large PN Junction also increases the forward current carrying capacity and reverse blocking voltage of the diode.

    The large signal diodes are not suitable for high frequency applications. The main applications of these diodes are in Power Supplies rectifiers, converter, inverters, battery charging devices, etc. In these diodes, the value of forward resistance is few Ohms and the value of reverse blocking resistance is in Mega Ohms. Since it has high current and voltage performance, these can be used in electrical devices which are used to suppress high peak voltages.

    First produced by Clarence Zener in , it is similar to normal diode in forward bias condition i. But in reverse bias condition, the diode conducts only when the applied voltage reaches the breakdown voltage, known as Zener Breakdown.

    It is designed to prevent the other semiconductor devices from momentary voltage pulses. It acts as voltage regulator. First production started in It undergoes electroluminescence process in which holes and electrons are recombined to produce energy in the form of light in forward bias condition. In the early days, LEDs are very costly and used only in special application.

    But over the years, the cost of the LEDs has comedown significantly. This and the fact they are extremely power efficient, makes LEDs as the main source of lighting in homes, offices, streets for street lighting as well as traffic lights , automobiles, mobile phones. The function of the diode is to regulate the voltage at a particular current.

    It functions as a two terminal current limiter. In this, JFET acts as current limiter to achieve high output impedance. The constant current diode symbol is shown below. Schottky Diode In this type of diode, the junction is formed by contacting the semiconductor material with metal. Due to this, the forward voltage drop is decreased to a minimum. The semiconductor material is N-type silicon, which acts as an anode and metals such as Chromium, Platinum, Tungsten etc.

    Due to the metal junction, these diodes have high current conducting capability and hence the switching time is reduced. So, Schottky Diode has greater use in switching applications. Mainly because of the metal — semiconductor junction, the voltage drop is low, which in turn increases the diode performance and reduces power loss.

    So, these are used in high frequency rectifier applications. The symbol of Schottky diode is as shown below. Shockley Diode It was one of the first semiconductor devices to be invented. Shockley Diode has four layers. It is also called as PNPN diode. It is equal to a thyristor without a gate terminal, which means the gate terminal is disconnected.

    As there is no trigger input, the only way the diode can conduct is by providing forward voltage. The diode has two operating states conducting and non-conducting. In non-conducting state the diode conducts with less voltage. The symbol of the Shockley diode is as follows: Shockley Diode Applications Acts as relaxation oscillator.

    Step Recovery Diodes It is also called as snap-off diode or charge-storage diode. These are the special type of diodes which stores the charge from positive pulse and uses in the negative pulse of the sinusoidal signals.

    The rise time of the current pulse is equal to the snap time. Due to this phenomenon, it has speed recovery pulses. The applications of these diodes are in higher order multipliers and in pulse shaper circuits. The cut-off frequency of these diodes is very high which are nearly at Giga hertz order.

    As multiplier, this diode has the cut-off frequency range of to GHz. In the operations which are performing at 10 GHz range, these diodes play a vital role. The efficiency is high for lower order multipliers. The symbol for this diode is as shown below. Tunnel Diode It is used as high-speed switch, with switching speed in the order of few nano-seconds.

    Due to tunneling effect it has very fast operation in microwave frequency region. It is a two-terminal device in which concentration of dopants is too high. The transient response is being limited by junction capacitance plus stray wiring capacitance. Mostly used in microwave oscillators and amplifiers.

    It acts as most negative conductance device. Tunnel diodes can be tuned both mechanically and electrically. The symbol of tunnel diode is as shown below. Tunnel Diode Applications.

    Diode is a semiconductor device which conducts only in forward biased. Zener diode is semiconductor device which can conduct in forward as well as reversed biased. Operation in Reverse Biased It gets damaged in reverse biased. It can operate without getting damaged. Circuit Symbol In normal diodes doping intensity is low. In Zener diode doping intensity is high to achieve sharp breakdown. Application Diode is used in rectifiers, clippers, clampers etc. Zener diode is mostly used in voltage regulator.

    Definition Diode A diode is formed by joining two layers of the semiconductor material, i. P-type layer and an N-type layer. The junction formed by joining these layers are called PN Junction. The P-type layer can also be understood as a positive layer because the majority charge carriers in a P-type layer are holes. Similarly, the N-type layer can also be considered as a Negative type layer because it consists of electrons as majority carriers.

    When the diode is forward biased, it does not start conduction instantaneously, but after a particular forward voltage, it starts conduction. This forward voltage is called the knee voltage of the diode. The value of knee voltage depends on the semiconductor material, for germanium it is 0.

    When the diode is reversed biased, the depletion region becomes broader. On the contrary, the thickness of depletion region decreases with increase in forward bias voltage. Therefore, in a reversed biased condition the depletion region does not let the current to flow across it. But the minority carriers can flow in reversed biased mode, constituting a small current in the diode. This is temperature dependent if the reverse voltage exceeds beyond a particular value the temperature increases and the minority carriers increases exponentially which can rupture the diode.

    Therefore, it is recommended that normal PN junction diode should be used in only forward biased mode. Zener Diode A Zener diode is doped properly thus the breakdown voltage can be modified by controlling the depletion width of the diode. This is the advantage of using a zener diode in reversed biased condition.

    A Zener diode is constructed in the similar manner by which conventional diode is constructed the only difference is the doping characteristics. When the zener diode is forward biased, it conducts in the similar fashion by which a normal diode conducts. When it is reversed biased, it conducts, and this makes the zener diode bidirectional semiconductor device. The zener diode can be understood by an equivalent circuit consisting of the voltage source and a resistor.

    The zener diode performs the same function. The higher the doping the narrow will be depletion width and the lower will be zener voltage. Thus, we can modify the width of the zener diode by appropriate doping and thus, the breakdown voltage can be modified. Thus, we can prevent the diode from breakdown by controlling the breakdown voltage. At the breakdown voltage, the diode does not burn out suddenly because the external resistance protects the current from flowing through the diode.

    Key Differences Between Diode and Zener Diode The direction of the current that the device allows creates a major difference between diode and zener diode.

    The diode conducts uni—directionally while the zener diode conducts bi—directionally in forward biased as well as in reverse biased. The doping characteristics of diode and zener diode are also different from each other.

    The zener diode is sharply doped while the conventional diode is moderately doped. The breakdown voltage in case of zener diode is sharp. But in normal PN junction diodes, the breakdown voltage is comparatively high A conventional diode cannot operate in reversed biased mode while the Zener diode can operate in reversed biased mode too. The Zener diode is generally used as a voltage regulator while the conventional diodes are used in the rectifier, clipper, clamper etc.

    Conclusion Diode and Zener diode, both are two terminal semiconductor device, but the crucial point which differentiates both is the ability to operate in reversed biased mode.

    Zener diodes are designed in a way so that they can operate in a reversed biased mode without getting damaged. On the contrary, a normal PN junction cannot be used for this purpose. Related Terms:.

    It is designed to prevent the other semiconductor devices from momentary voltage pulses. It acts as voltage regulator. First production started in It undergoes electroluminescence process in which holes and electrons are recombined to produce energy in the form of light in forward bias condition.

    In the early days, LEDs are very costly and used only in special application. But over the years, the cost of the LEDs has comedown significantly. This and the fact they are extremely power efficient, makes LEDs as the main source of lighting in homes, offices, streets for street lighting as well as traffic lightsautomobiles, mobile phones. The function of the diode is to regulate the voltage at a particular current.

    It functions as a two terminal current limiter. In this, JFET acts as current limiter to achieve high output impedance. The constant current diode symbol is shown below. Schottky Diode In this type of diode, the junction is formed by contacting the semiconductor material with metal. Due to this, the forward voltage drop is decreased to a minimum. The semiconductor material is N-type silicon, which acts as an anode and metals such as Chromium, Platinum, Tungsten etc.

    Due to the metal junction, these diodes have high current conducting capability and hence the switching time is reduced.

    How Schottky Diodes Work

    So, Schottky Diode has greater use in switching applications. Mainly because of the metal — semiconductor junction, the voltage drop is low, which in turn increases the diode performance and reduces power loss. So, these are used in high frequency rectifier applications. The symbol of Schottky diode is as shown below.

    Difference between Diode and Zener Diode

    Shockley Diode It was one of the first semiconductor devices to be invented. Shockley Diode has four layers. It is also called as PNPN diode. It is equal to a thyristor without a gate terminal, which means the gate terminal is disconnected. As there is no trigger input, the only way the diode can conduct is by providing forward voltage.

    Types of Diodes | Small Signal, LED, Schottky, Zener

    The diode has two operating states conducting and non-conducting. When the diode is forward biased, it does not start conduction instantaneously, but after a particular forward voltage, it starts conduction. This forward voltage is called the knee voltage of the diode.

    The value of knee voltage depends on the semiconductor material, for germanium it is 0. When the diode is reversed biased, the depletion region becomes broader. On spectrum remote codes contrary, the thickness of depletion region decreases with increase in forward bias voltage.

    Therefore, in a reversed biased condition the depletion region does not let the current to flow across it. But the minority carriers can flow in reversed biased mode, constituting a small current in the diode. This is temperature dependent if the reverse voltage exceeds beyond a particular value the temperature increases and the minority carriers increases exponentially which can rupture the diode. Therefore, it is recommended that normal PN junction diode should be used in only forward biased mode.

    Zener Diode A Zener diode is doped properly thus the breakdown voltage can be modified by controlling the depletion width of the diode. This is the advantage of using a zener diode in reversed biased condition. A Zener diode is constructed in the similar manner by which conventional diode is constructed the only difference is the doping characteristics.

    When the zener diode is forward biased, it conducts in the similar fashion by which a normal diode conducts. When it is reversed biased, it conducts, and this makes the zener diode bidirectional semiconductor device. With its lower forward voltage drop, the Schottky diode consumes only 0. If our load required 1. Other advantages for using a Schottky diode over a regular diode include: Faster recovery time. The small amount of charge stored within a Schottky diode makes it ideal for high speed switching applications.

    Less noise. The Schottky diode will produce less unwanted noise than your typical p-n junction diode. Better performance. The Schottky diode will consume less power and can easily meet low-voltage application requirements. There are some disadvantages to keep in mind about Schottky diodes. A reverse-biased Schottky diode will experience a higher level of reverse current than a traditional diode. This will lead to more leaked current when connected in reverse. Schottky diodes also have a lower maximum reverse voltage than standard diodes, usually 50V or less.

    Once this value is exceeded then the Schottky diode will break down and start to conduct a large amount of current in reverse. However, even before reaching this reverse value the Schottky diode will still leak a small amount of current like any other diode. How a Schottky Diode Works A typical diode combines p-type and n-type semiconductors to form a p-n junction.

    In a Schottky diode metal replaces the p-type semiconductor. This metal can range from platinum to tungsten, molybdenum, gold, etc. When metal is combined with an n-type semiconductor an m-s junction is formed.

    This junction is referred to as a Schottky Barrier. The behavior of the Schottky Barrier will differ depending on whether the diode is in an unbiased, forward-biased, or reverse-biased state.


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