Diode

Diode is also called crystal diode, abbreviation diode (diode), It only into one direction passes electricity electronic parts. It is one kind has 1 part number reveal the 2 terminal devices, according to an external voltage is the direction of current flow or not, the flow of nature. Crystal diode as a p type semiconductor and n-type semiconductor formed p - n knot, in its interface between both sides formed space charge layer, and built a self-built electric fields. When there is no an external voltage, due to p - n knot on both sides of the spread of poorer cause carrier concentration and self-built electric current caused in the electric current equal drift balance.

The diode characteristics

Diode is one kind has the unidirectional conductive two ends device, electronic diode and crystals diode parts, electronic diode now is rarely seen, commonner and commonly used much is crystal diode. The diode one-way conductive properties, almost all the electronic circuit, all want to use a diode, in many of the circuit, it plays an important role, it is one of the earliest birth of semiconductor devices, its application is also very [1] widely.

The diode pipe pressure drop: silicon diode (not emit light type) positive pipe pressure drop 0.7 V, germanium tube positive pipe pressure drop of 0.3 V, light emitting diode positive pipe pressure drop for along with different emitting light colors and different.

The diode voltage and current is not linear relationship, so in different diode connected in parallel to connect adaptation of the resistance.

The diode characteristic curve

As with PN junction, diode has unilateral electrical conductivity. In a diode add have positive voltage, when voltage value is lesser, current dinky; When the voltage exceed 0.6 V, the current began to increase exponentially rule, usually call this the diode is open voltage, When the voltage to about 0.7 V, diode is completely on-state, usually says the voltage of diode conduction voltage, use symbols UD said.

For ge diode, open voltage 0.2 V, conduction voltage UD about 0.3 V.

In a diode with a reverse voltage, when voltage value IS lesser, current, its current value for minimal reverse current IS saturated. When reverse voltage exceeds a certain value, the current began increasing rapidly, called backward breakdown, says the voltage of the diode reverse breakdown voltage, use symbols UBR said. Different types of diode breakdown voltage of UBR value difference is very big, from dozens of volts to several kv.

The diode reverse breakdown

Zener breakdown

According to the mechanism of reverse breakdown into zener breakdown and an avalanche breakdown two circumstances. In high doping concentration of circumstances, for potential barrier area width is small, reverse voltage is bigger, destroy the potential barrier zone covalent bond structure, make covalence from covalent bond bondage, generate electrons - hole, causing a sharp increase of current, the breakdown called zener breakdown. If doping concentration lower, potential barrier area width wider, not easy to produce zener breakdown.

Avalanches breakdown

Another kind of breakdown for avalanche breakdown. When reverse voltage increases to larger value, electrode-biology make ShaoZi drifting velocity speeded up, thus the covalence collide with a single, covalence knock the covalent bond, create new electronic - hole right. New generated by electric acceleration - hole again after other covalence, hit an avalanche carriers to increase, cause current increased dramatically, this breakdown called avalanche breakdown. No matter which kind of breakdown, if no restrictions on its current PN junction, might cause permanent damage.

The diode is used

1, rectifier diode

Using diode one-way conductivity, can change the direction variations of alternating current transform into a single direction of pulse direct current.

2, switch components

Diode in forward voltage resistance is very small, in under the action of on-state, equivalent to a connect with the switch; In reverse voltage, resistance is very big, role in cut-off state, like a disconnect switch. Using diode switches characteristic, and can be composed of various logic circuit.

3, limiting components

Diode is the wizard tong, its positive pressure drop basic unchanged (silicon tube is 0.7 V, germanium tube of 0.3 V). Use this one character, in a circuit as limiting element, can the signal amplitude limit within a certain range.

4, following the flow diode

The switch power inductor and perceptual load such as relays plays following flow function.

5, detection diode

In radio plays detection function.

6 and transfiguration diode

Used in television high-frequency tuner.

7, display elements

Used for VCD, DVD, calculator, etc on the display.

8, avr diode

Reverse breakdown voltage is constant, and breakdown but later return, using this feature can be realized voltage circuit.

Diode principle of work

Crystal diode as a p type semiconductor and n-type semiconductor formed p - n knot, in its interface between both sides formed space charge layer, and built a self-built electric fields. When there is no an external voltage, due to p - n knot on both sides of the spread of poorer cause carrier concentration and self-built electric current caused in the electric current equal drift balance. When outside have positive voltage offset, external electric field and self-built electric field of mutual inhibitory action to make carriers diffusion extinction caused a current increasing positive current. When the outside has reverse voltage offset, external electric field and self-built electric field further strengthen, form in certain reverse voltage range and reverse bias voltage irrelevant reverse saturated current I0. When additional reverse voltage high to certain degree, p - n "space charge planes of electric field intensity reach critical value produce carriers multiply process, producing a large amount of electronic cavitation, produced numerical big reverse breakdown current, called the diode breakdown phenomenon. P - n "reverse breakdown have zener breakdown and an avalanche breakdown of points.

Diode type

There are many kinds, according to the diode used semiconductor materials, can be divided into germanium diode (Ge tube) and silicon diode (Si tubes). According to their different USES, can be divided into detection diode, rectifier diode, avr diode, switch diode, segregation diode, schottky diodes, light emitting diode, silicon power switching diodes, rotating diodes. According to the tube core structure, can divide again for contacts type diode, surface contact type diode or flat-screen diode. Contacts with a piece of diode is very fine wires pressure in clean of semiconductor wafer surface, ventilation to pulse current, make contact wire end with chip firmly sintering together, form a "PN junction". Because be contacts are only allowed by the current (not less than decades ma), for high-frequency small current circuit, such as radio detection, etc. Surface contact type of the diode's "PN junction" area is larger, allowing the large current (a few Ann to dozens of Ann), mainly used for ac to dc "transformation" rectifier circuit. Flat-screen diode is a kind of tailor-made silicon diode, it can not only through large current, and stable and reliable performance, more for switch, pulse and high-frequency circuits.