Vi Charcteristics of pn junction diode.pptx

This ppt gives brief information about Vi characteristics of Pn junction diode

1. V-I Characteristics of PN Junction Diode The V-I characteristics of PN junction diodes is a fundamental piece of knowledge. This presentation will guide you through the basics of this essential component and its applications. AA Ch. Ajay

2. Introduction to PN Junction Diode Structure The PN junction diode is a two-terminal semiconductor device that has a P-type and N-type semiconductor material in close contact. Conduction It allows the flow of electrical current in one direction while blocking the flow in the opposite direction. This is due to the fact that P-type semiconductor material has a surplus of holes (positive charge) and N-type material has a surplus of electrons (negative charge). Symbol The arrowhead indicates the direction of the flow of current when the diode is forward-biased.

3. What are V-I Characteristics? 1 Voltage-Current Characteristics The V-I characteristics of a diode describe how it acts as an electrical component by showing the relationship between the voltage (V) and current (I) flowing through it. 2 Forward Bias When a diode is forward-biased, the voltage across the diode (V) increases and the current through the diode (I) increases exponentially. 3 Reverse Bias In reverse-bias, a small reverse leakage current flows called the reverse saturation current (I0).

4. Forward Bias Characteristics Low Voltage Region When a small forward voltage (V) is applied and increased gradually, a small current (I) flows in the diode. This low voltage region is called the Knee voltage. High Voltage Region After reaching the knee voltage, the current increases exponentially with a further increase in V, while the diode voltage remains almost constant. Saturation Region The region where the current reaches saturation is called the saturation region. At this point, the diode behaves almost like a short circuit.

5. Reverse Bias Characteristics Reverse Bias In reverse-bias, the minority carriers in the P and N regions are present closer to the junction. They get repelled by the external voltage and move away from the junction. This causes the depletion layer to increase in width. Avalanche Breakdown At very high reverse voltages, the electric field intensifies to a level that knocks electrons from the covalently bonded atoms in the depletion layer. This frees up more electrons leading to an avalanche effect in the depletion region leading to breakdown.

6. Breakdown Voltage 1 Zener Effect The breakdown in a PN Junction diode takes place when the reverse voltage is increased beyond a particular limit, called the Zener voltage. This causes the depletion region to collapse and current starts flowing. 2 Impact Ionization If the applied reverse voltage is too high, strong electric fields can cause some electrons to gain enough energy to knock other electrons off their atoms, creating more current beyond the Zener voltage.

7. Temperature Effects on V-I Characteristics Forward Bias Increasing temperature increases the forward current and decreases the forward voltage. This effect is attributed to the decrease in the diode's effective resistance with increasing temperature and an increase in the number of electrons available for conduction. Reverse Bias In reverse bias, temperature increases cause an increase in reverse leakage current, whereas at high temperatures, the voltage needed to cause avalanche breakdown decreases.

8. Applications of PN Junction Diode Rectification P-N junction diodes are used in electronic circuits as rectifiers that convert AC current into DC current. This makes them useful for a wide range of electronic devices, from power supplies to LED lighting systems. Voltage Regulation Zener diodes, a type of P-N junction diodes, are used in power supplies and other electronic circuits to provide a constant voltage or to regulate voltage fluctuations. Sensing Photodiodes are P-N junction diodes that generate a voltage when exposed to light and can be used in various sensors like optical communication, autofocus cameras, and other industrial applications. Oscillation The PN junction diode can also be used in an oscillator circuit, converting DC into an AC signal, which results in applications in radio communication, audio, and other electronic devices.

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