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Transistor as a Switch
Transistor as an Amplifier
n-channel JFET and p-channel JFET
Applications of FET
Integrated Circuits | Types of IC
Regulated Power Supply
Laser | Types and Components of Laser
Mobility of Charge Carrier
Sinusoidal Wave Signal
Common Emitter Amplifier
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PN Junction Diode
Half Wave Diode Rectifier
Full Wave Diode Rectifier
Diode Bridge Rectifier
Application of Zener Diode
LED or Light Emitting Diode
PIN Photodiode | Avalanche Photodiode
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Reverse Recovery Time of Diode
MOSFET | Working Principle of p-channel n-channel MOSFET
MOS Capacitor | MOS Capacitance C V Curve
Applications of MOSFET
MOSFET as a Switch
Half Wave Rectifiers
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Theory of Semiconductor
Energy Bands of Silicon
Impurities in Semiconductor
Conductivity of Semiconductor
Intrinsic Silicon and Extrinsic Silicon
P Type Semiconductor
N Type Semiconductor
P N Junction
Bias of P N Junction
Gallium Arsenide Semiconductor
DIAC Construction Operation and Applications of DIAC
Construction of DiacIt is a device which consists of four layers and two terminals. The construction is almost same as that of the transistor. But there are certain points which deviate from the construction from the transistor. The differentiating points are-
- There is no base terminal in the diac.
- The three regions have almost the same level of doping.
- It gives symmetrical switching characteristics for either polarity of voltages.
Operation of DiacFrom the figure, we see that it has two p-type material and three n-type materials. Also it does not have any gate terminal in it. The diac can be turned on for both the polarity of voltages. When A2 is more positive with respect to A1 then the current does not flows through the corresponding N-layer but flows from P2-N2-P1-N1. When A1 is more positive A2 then the current flows through P1-N2-P2-N3.
The construction resembles the diode connected in series. When applied voltage is small in either polarity, a very small current flows which is known as leakage current because of drift of electrons and holes in the depletion region. Although a small current flows, but it is not sufficient enough to produce avalanche breakdown so the device remains in the non conducting state. When the applied voltage in either polarity exceeds the breakdown voltage, diac current rises and the device conducts in accordance with its V-I characteristics. The V-I characteristics resembles the english word Z. The diac acts as open circuit when the voltage is less than its avalanche breakdown voltage. When the device has to be turned off, the voltage must be reduced below its avalanche breakdown voltage.
Application of DiacIt can be used mainly in the triac triggering circuit. The diac is connected in the gate terminal of the triac. When the voltage across the gate decreases below a predetermined value, the gate voltage will be zero and hence the triac will be turned off. The main applications are-
- It can be used in the lamp dimmer circuit.
- It is used in the heat control circuit.
- It is used in the speed control of a universal motor.
Conclusion of DiacThe diac is an important device in the thyristor family. The main advantage of using this device is-
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