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Avalanche diode

 

 
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Avalanche diode
 
 
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An avalanche diode is a diode
Diode

In electronics, a diode is a two-terminal device .Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional electric current property....
 (usually made from silicon
Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
, but can be made from another semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
) that is designed to go through avalanche breakdown
Avalanche breakdown

Avalanche breakdown is a phenomenon that can occur in both Electrical insulation and Semiconductor materials. It is a form of electric current multiplication that can allow very large currents to flow within materials which are otherwise good insulators....
 at a specified reverse bias voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
 and conduct as a type of voltage reference
Voltage reference

A voltage reference is an electronic device that produces a fixed voltage irrespective of the loading on the device, power supply variation and temperature....
.

The Zener diode
Zener diode

A Zener diode is a type of diode that permits electric current in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as "Zener knee voltage" or "Zener voltage"....
 exhibits an apparently similar effect, but its operation is caused by a different mechanism, called Zener breakdown. Both effects are actually present in any such diode, but one usually dominates the other.






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Encyclopedia


An avalanche diode is a diode
Diode

In electronics, a diode is a two-terminal device .Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional electric current property....
 (usually made from silicon
Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
, but can be made from another semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
) that is designed to go through avalanche breakdown
Avalanche breakdown

Avalanche breakdown is a phenomenon that can occur in both Electrical insulation and Semiconductor materials. It is a form of electric current multiplication that can allow very large currents to flow within materials which are otherwise good insulators....
 at a specified reverse bias voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
 and conduct as a type of voltage reference
Voltage reference

A voltage reference is an electronic device that produces a fixed voltage irrespective of the loading on the device, power supply variation and temperature....
.

The Zener diode
Zener diode

A Zener diode is a type of diode that permits electric current in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as "Zener knee voltage" or "Zener voltage"....
 exhibits an apparently similar effect, but its operation is caused by a different mechanism, called Zener breakdown. Both effects are actually present in any such diode, but one usually dominates the other. Zener diodes are typically restricted to a few tens of volts maximum, but silicon avalanche diodes are available with breakdown voltages of over 4000 V.

Uses


Protection


A common application is protecting electronic circuit
Electronic circuit

An electronic circuit is a closed path formed by the interconnection of electronic components through which an electric current can flow. The electronic circuits may be physically constructed using any number of methods....
s against damaging high voltages
Overvoltage

When the voltage in a Electrical network or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous....
. The avalanche diode is connected to the circuit so that it is reverse-biased. In other words, its cathode
Cathode

A cathode is an electrode through which electric charge flows out of a polarized electrical device. Mnemonic: CCD .From an electrochemical point of view, positively charged ion invariably move toward the cathode and/or negatively charged ion move away from it to balance the electrons arriving from external circuitry....
 is positive with respect to its anode
Anode

An anode is an electrode through which electric charge flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the positive electric current....
. In this configuration, the diode is non-conducting and does not interfere with the circuit. If the voltage increases beyond the design limit, the diode suffers avalanche breakdown
Avalanche breakdown

Avalanche breakdown is a phenomenon that can occur in both Electrical insulation and Semiconductor materials. It is a form of electric current multiplication that can allow very large currents to flow within materials which are otherwise good insulators....
, causing the harmful voltage to be conducted to earth. When used in this fashion they are often referred to as clamper diodes because they "clamp" the voltage to a predetermined maximum level. Avalanche diodes are normally specified for this role by their clamping voltage VBR and the maximum size of transient they can absorb, specified by either energy (in joule
Joule

The joule is the SI derived unit of energy in the International System of Units. It is defined as:One joule is the amount of energy required to perform the following actions:...
s) or . Avalanche breakdown is not destructive, as long as the diode is not allowed to overheat.

RF noise generation


Avalanche diodes generate radio frequency
Radio frequency

Radio frequency is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves....
 noise; they are commonly used as noise sources in radio equipment. For instance, they are often used as a source of RF for antenna analyzer
Antenna analyzer

An antenna analyzer is a device used for measuring the efficiency of antenna systems in radio electronics applications....
 bridges. Avalanche diodes can also be used as white noise
White noise

White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency....
 generators.

See also

  • Transient voltage suppression diode
    Transient voltage suppression diode

    A transient voltage suppression diode is an electronic component used to protect sensitive electronics from voltage spikes induced on connected wires....