Characteristics of diac

What is diac and DIAC? Is diode characteristic symmetrical? Some other applications of a DIAC include: It can be used in the lamp dimmer circuit. It is used in a heat control circuit.

V-I characteristics of a diac is shown below.

Characteristics of DIAC. Volt-ampere characteristic of a diac is shown in figure. Its looks like a letter Z due to symmetrical switching characteristics for each polarity of the applied voltage. 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 Aand Aor main terminal MTand MT2. Typical DIAC voltage and current relationships. V BO is the breakover voltage.

Construction: The basic arrangement of the semiconductor layers of the diac is shown in Figure.

Note that neither terminal is referred to as the cathode. Instea there is an anode (or electrode 1) and an anode (or electrode 2). When anode is positive with respect to anode the semiconductor. It exhibits negative resistance characteristics.

The Conduction Current rises quickly and hence Resistance is connected in series with a DIAC for a safe operating level of the circuit. Diac is made up of three layers of N-type and P-type semiconductors , like a transistor, but because of its doping, it does not behave as a transistor. Thus, it is a bidirectional device and conducts in both directions, suitable for AC electricity. It resembles the English letter Z because of the symmetrical switching characteristics for either polarity of the applied voltage. The name DIAC comes from the words DI ode AC switch.

A DIAC is basically a low-current TRIAC without a gate terminal. Two different DIAC symbols in general use are shown in Fig. DIAC characteristics are illustrated in Fig. There is no control terminal on this device. Physically it looks like a regular semiconductor diode.

Figure A shows symbol and structure of the Diac. The two terminals of the DIAC is labeled as MTand MT2.

Diac : Type of semiconductor device. It acts as a diode for alternating current, restricting the current until the certain voltage is reached and then it conducts normally. The DIAC is obtained form Diode works on AC. Breakover voltage: Voltage below which a diac or a triac is not conducting, but when the voltage surpasses that conduction starts.

The term DIAC stands for the DIode for Alternating Current ( DIAC ), it is a bidirectional semiconductor switch that can be turned ON in both forward and reverse direction. The device is a member of the Thyristor family and it is mostly used in triggering TRIAC and other Thyristor based circuits. The characteristics curve is shown in the below Diagram. Switch-on is effected by raising the applied voltage to the breakover voltage.

In above figure a simple DIAC TRIAC Power circuit is shown, the working of this circuit is can be. DIAC , Diode AC bi-directional switch is widely used with TRIACs to improve the fact that its switching characteristic is far more even than that of the TRIAC. The diac is a two-terminal bidirectional device.