In high-voltage applications, high-voltage diodes are used. Diodes of high voltage come in a variety of types based on their construction.
Diodes and Their Types
In this article we will discuss some of the most important high voltage diodes currently available.
The PN Junction Diode
General-purpose diodes are PN junction diodes. Zener diodes work by applying a higher voltage to the N material than the P material in reverse bias. Until a certain voltage is applied to the Zener diode (the Zener voltage or avalanche voltage), the diode acts as a normal rectifier. It produces a large current when this happens.
Diodes with Pins
A PIN diode is a three-layer semiconductor diode made from a heavily doped layer P and a heavily doped layer N sandwiched in between. Charges stored in the integral layer determine the resistance of the diode at RF and microwave frequencies, along with other parameters of the diode. The resistance is typically between kilohms and less than 1 ohm for a given diode.
The high voltage diode 2CL2FL can be used as a switch or as an attenuator. The devices in which RF diodes are used include stereo amplifiers, radio transmitters, television monitors, and other devices using radio frequency or microwave signals.
Televisions (TVS) are semiconductors that limit overvoltages during transient conditions. Diodes that limit current over a wide range of voltage are called current limiting diodes (CLD). A Gunn diode is a transfer electron device. It has a negative resistance region. A IMPATT diode is a high voltage diode that operates at a very high frequency and power.
Diodes Schottky at High Voltages
Fast-switching and high frequency applications require Schottky barrier diodes. The simplest form of these devices consists of a metal layer that contacts a semiconductor. There is a rectifying property in this metal junction (i.e., the current passes through it with one polarity more readily than the other).
Fast-switching and high-frequency applications are where Schottky diodes are used. These diodes do not leak reverse current because they only operate with the majority of carriers.
Conduction-band electrons are heavily populated in the metal region of Schottky diodes. This region is lightly doped with semiconductor electrons on the N-type side. Electrons in the N-region, which have a higher energy, are injected into the metal region, where they quickly lose their excess energy.
In contrast to conventional rectifier diodes, where there are minority carriers, this rectifier diode responds very rapidly to a change in bias. The benefit of Schottky diodes is to decrease switching time, which makes them popular in high-frequency applications. A Schottky diode is also known as a hot carrier diode.
Varactor Diodes With High Voltages
Diodes with P-N junctions, referred to as varactor diodes, serve as voltage-controlled capacitors under reverse bias. The PN junction has a built-in capacitance. The reverse bias of the junction reduces the effective capacitance and increases the distance between the two “plates” of the capacitor when the voltage is increased. It is possible to control capacitance range and way-capacitance by adjusting the doping gradient and junction width.
Capacitance ranges of four to one are not problematic. At zero bias, a varactor diode (or “varicap diode”) might have 60 picofarads (pf) of resistance, and at 20 volts (V) it might only have 15 pf. A ten-to-one capacitance range is possible with precision manufacturing. The use of varactor diodes in electronic tuning systems can eliminate the need for moving parts and reduce the use of moving parts.
The Performance Specifications of High Voltage Diodes
- It is the maximum level of repetitive reverse voltage that can be applied in an instant.
- During reverse voltage application, reverse current is the value of the current.
- If the reverse voltage is applied while the device is conducting in the forward direction, the reverse recovery time is the time it takes for the reverse current to reach a specified level.
- Forward voltage occurs when current flows in the forward direction across the diode terminals.
- The power dissipated by a high voltage diode while it is on is called dissipation.
- High voltage diodes are designed to operate between a range of junction operating temperatures.
