DinizApp/Electronics Center

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In this AC circuit, SCR turns off when we turn off the GATE, that’s because current always reaches “0V” in phase changes. In direct current is necessary turn off or divert the source, taking SCR to not conduct.

In this AC circuit, SCR turns off when we turn off the GATE, that’s because current always reaches “0V” in phase changes.
In direct current is necessary turn off or divert the source, taking SCR to not conduct.

Neste circuito em corrente alternada o SCR desliga quando desligamos o Gate, pois a corrente atinge o "0V" sempre nas mudanças de fase.
Se a corrente for contínua é necessário desligar a alimentação ou desvia-la, levando o SCR a não conduzir.
114

The DIAC, or "diode for alternating current", is a diode that conducts electrical current only after its breakover voltage has been reached momentarily. When breakdown occurs, the diode enters a region of negative dynamic resistance, leading to a decrease in the voltage drop across the diode and, usually, a sharp increase in current through the diode. The diode remains in conduction until the current through it drops below a value characteristic for the device, called the holding current. Below this value, the diode switches back to its high-resistance, non-conducting state. This behavior is bidirectional, meaning typically the same for both directions of current. Most DIACs have a three-layer structure with breakover voltage of approximately 30 V. Their behavior is similar to that of a neon lamp, but it can be more precisely controlled and takes place at a lower voltage. DIACs have no gate electrode, unlike some other thyristors that they are commonly used to trigger, such as TRIACs and SCRs. DIACs are also called "symmetrical trigger diodes" due to the symmetry of their characteristic curve. Because DIACs are bidirectional devices, their terminals are not labeled as anode and cathode but as A1 and A2 or main terminal MT1 and MT2. (It is similar to two Zener diodes connected in series. It is possible to produce an equivalent DIAC of 9V, for example, connecting two Zener diodes of 9V in (anti)series, cathode with cathode and anode with anode). The circuit above shows how to test a DIAC, notice that it conducts when reaches 30V and the voltage drops to 0, behaving like a short-circuit or a closed switch.

The DIAC, or "diode for alternating current", is a diode that conducts electrical current only after its breakover voltage has been reached momentarily.
When breakdown occurs, the diode enters a region of negative dynamic resistance, leading to a decrease in the voltage drop across the diode and, usually, a sharp increase in current through the diode. The diode remains in conduction until the current through it drops below a value characteristic for the device, called the holding current. Below this value, the diode switches back to its high-resistance, non-conducting state. This behavior is bidirectional, meaning typically the same for both directions of current.
Most DIACs have a three-layer structure with breakover voltage of approximately 30 V. Their behavior is similar to that of a neon lamp, but it can be more precisely controlled and takes place at a lower voltage.
DIACs have no gate electrode, unlike some other thyristors that they are commonly used to trigger, such as TRIACs and SCRs.
DIACs are also called "symmetrical trigger diodes" due to the symmetry of their characteristic curve. Because DIACs are bidirectional devices, their terminals are not labeled as anode and cathode but as A1 and A2 or main terminal MT1 and MT2.

(It is similar to two Zener diodes connected in series. It is possible to produce an equivalent DIAC of 9V, for example, connecting two Zener diodes of 9V in (anti)series, cathode with cathode and anode with anode).
The circuit above shows how to test a DIAC, notice that it conducts when reaches 30V and the voltage drops to 0, behaving like a short-circuit or a closed switch.

O DIAC, ou Diode for Alternating Current, é um gatilho bidirecional, ou diodo que conduz corrente apenas após a tensão de disparo ser atingida, e para de conduzir quando a corrente elétrica cai abaixo de um valor característico, chamada de corrente de corte. Este comportamento é o mesmo nas duas direções de condução de corrente. A tensão de disparo é por volta dos 30 volts para a maioria destes dispositivos. Este comportamento é de certa forma similar, porém mais precisamente controlado e ocorrendo em menor valor, ao comportamento de uma lâmpada de neon.

O DIAC é normalmente usado para disparar TRIACs e SCRs.

Como um DIAC é um gatilho bidirecional, seus terminais não são marcados como anodo ou catodo mas a maioria é marcada como A1 ou MT1 e A2 ou MT2.

(Funciona da mesma maneira que dois diodos zener em Série. Pode-se produzir um DIAC equivalente de 9V, por exemplo, ligando dois diodos zener de 9v em (anti)série, cátodo com cátodo e ânodo com ânodo).
O circuito acima mostra como devemos testar um Diac, observe que quando atinge os 30v ele entra em condução e a tensão vai a zero, se comportando como um curto circuito ou uma chave fechada.
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The DIAC is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities. DIode Alternating Current (DIAC) is widely used to assist even triggering of a TRIAC (or a thyristor). DIAC is composed by three layers (PNP), very much similar to a transistor, however, the doping concentrations in N –type crystal are different. A pair of diodes of four layers in parallel is an equivalent circuit of a DIAC. Typically the DIAC is placed in series with the gate of a TRIAC. DIACs are often used in conjunction with TRIACs because these devices do not fire symmetrically as a result of slight differences between the two halves of the device.
The DIAC is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities. DIode Alternating Current (DIAC) is widely used to assist even triggering of a TRIAC (or a thyristor). DIAC is composed by three layers (PNP), very much similar to a transistor, however, the doping concentrations in N –type crystal are different. A pair of diodes of four layers in parallel is an equivalent circuit of a DIAC. Typically the DIAC is placed in series with the gate of a TRIAC. DIACs are often used in conjunction with TRIACs because these devices do not fire symmetrically as a result of slight differences between the two halves of the device.

Um diac é um comutador de onda completa ou bidireccional que dispara nos dois sentidos e ambas as polaridades. Diac significa (diode AC switch – diodo comutador AC). O diac é usado normalmente para activar um Triac ou um Tiristor. É composto por três camadas (PNP), a sua construção assemelha-se a de um transístor bipolar, porém difere na dopagem do cristal N. O circuito equivalente de um diac é um par de díodos de quatro camadas em paralelo. O diac é colocado tipicamente em série com a porta (GATE) de um TRIAC. Os Diacs são usados frequentemente em conjunto com TRIAC porque estes dispositivos não disparam simetricamente em consequência das ligeiras diferenças entre as duas partes do dispositivo.
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117

The phenomenon of conductivity in only one direction is used as an electrical current switching for rectification of half-wave, so, this is the most used diode effect in electronics, because allows the current to flow between its terminals in only one direction. This property is used in many electronic circuits (and rectifiers). A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. At some point, the potential formed by the pn junction don’t allow the electrons and gaps move.

The phenomenon of conductivity in only one direction is used as an electrical current switching for rectification of half-wave, so, this is the most used diode effect in electronics, because allows the current to flow between its terminals in only one direction. This property is used in many electronic circuits (and rectifiers).
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.
At some point, the potential formed by the pn junction don’t allow the electrons and gaps move.

O fenômeno da condutividade em um só sentido é aproveitado como um chaveamento da corrente elétrica para a retificação de sinais senoidais, portanto, este é o efeito diodo semicondutor tão usado na eletrônica, pois permite que a corrente flua entre seus terminais apenas numa direção. Esta propriedade é utilizada em grande número de circuitos eletrônicos e nos retificadores.
Os retificadores são circuitos elétricos que convertem a tensão CA (AC) em tensão CC (DC). CA vem de Corrente alternada, significa que os elétrons circulam em dois sentidos, CC (DC), Corrente contínua, isto é circula num só sentido.
A certa altura, o potencial U , formado a partir da junção n e p não deixa os elétrons e lacunas movimentarem-se, este processo dá-se devida assimetria de cargas existente.

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