Application of Junction Diode as a Rectifier – Class 12 | Chapter – 14 | Physics Short Notes Series PDF for NEET & JEE
Junction Diode as a Rectifier: A junction diode can be used as a rectifier to convert AC (alternating current) voltage to DC (direct current) voltage. In a rectifier circuit, the diode is placed in series with the load resistor and the AC source. When the AC voltage is positive, the diode is forward-biased and allows current to flow through the load resistor. When the AC voltage is negative, the diode is reverse-biased and does not allow current to flow through the load resistor. As a result, the output voltage across the load resistor is unidirectional and has a similar waveform to the input voltage but with negative half-cycles removed.
A junction diode is well-suited for use as a rectifier because it has a low forward voltage drop and a high reverse breakdown voltage. The low forward voltage drop means that the diode will conduct easily when forward-biased, resulting in a low voltage drop across the load resistor and a high output voltage. The high reverse breakdown voltage means that the diode will not break down and conduct in the reverse direction when the input voltage is negative.
Rectifiers are widely used in power supplies, battery chargers, and other electronic circuits where DC voltage is needed. By using a junction diode as a rectifier, a simple and efficient circuit can be created to convert AC voltage to DC voltage.
Advantages of Junction Diode as a Rectifier
Junction diodes offer several advantages when used as rectifiers in electronic circuits:
- Low voltage drop: Junction diodes have a low forward voltage drop, typically around 0.7 volts for silicon diodes and 0.3 volts for germanium diodes. This means that they can conduct easily when forward-biased, resulting in a low voltage drop across the load resistor and a high output voltage.
- High reverse breakdown voltage: Junction diodes have a high reverse breakdown voltage, which means that they can withstand a high reverse voltage without breaking down and conducting in the reverse direction. This makes them well-suited for use as rectifiers in high-voltage applications.
- Efficiency: Because junction diodes have a low forward voltage drop, they are more efficient than other types of rectifiers, such as bridge rectifiers or voltage regulators.
- Simple and reliable: Junction diodes are simple to use and require few components, which makes them a reliable and cost-effective choice for rectification applications.
- Small size: Junction diodes are small in size and can be easily integrated into circuits with limited space.
Disadvantages of Junction Diode as a Rectifier
While junction diodes have several advantages when used as rectifiers, they also have some disadvantages:
- Limited current carrying capacity: Junction diodes have a limited current carrying capacity, which means that they are not suitable for high-power applications. If the current exceeds the diode’s maximum rated current, the diode can overheat and become damaged.
- Limited voltage handling capability: Junction diodes have a limited voltage handling capability, which means that they are not suitable for high-voltage applications. If the voltage exceeds the diode’s maximum rated voltage, the diode can break down and become damaged.
- Temperature dependence: The forward voltage drop of a junction diode is temperature dependent. As the temperature increases, the forward voltage drop decreases. This can affect the performance of the diode and the circuit in which it is used.
- Reverse recovery time: When a junction diode switches from forward-biased to reverse-biased, there is a brief period of time during which the diode continues to conduct in the forward direction. This is known as the reverse recovery time and can be a limiting factor in high-frequency rectifier circuits.
- Non-linear output: The output of a junction diode rectifier is not perfectly smooth, as it still contains some AC ripple. This can be a disadvantage in circuits where a very stable DC output is required.
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