Class 12 Physics Semiconductor Electronics Fullwave Rectifier

Fullwave Rectifier

Circuit Diagram:

• The main difference between half and full wave rectifier in circuit, is the usage of two diodes – D1 and D2

Input and Output:

Working:

Case 1

• During the positive half of the input cycle of AC voltage, the junction diode D1 is forward biased as shown in the diagram above
• Hence, current flows in the above circuit as indicated
• The diode D2 is reverse biased and hence no current due to D2
• We get output when the same is measured across the load resistance RL due to the diode D1 alone

Case 2

The circuit diagram for the negative half of the input cycle of AC voltage:

• During the positive half of the input cycle of AC voltage, the junction diode D2 is forward biased as shown in the diagram above
• Hence, current flows in the above circuit as indicated
• The diode D1 is reverse biased and hence no current due to D1
• We get output when the same is measured across the load resistance RLdue to the diode D2 alone
1. We observe that one of the diode conducts and the flow of current across the load resistance is in the same direction
2. Also, current flows during both cycles of the input AC voltage. However, the output though unidirectional has ripple contents. Ripple contents indicate both AC and DC components
3. We can get only the DC component by passing it through a filter circuit
4. The filter circuit consists of Resistance and Capacitance

Circuit Diagram:

• C has a high capacitance value and serves as a filter circuit
• RL is a load resistance

Working:

• The capacitance offers low impedance to AC component and offers infinite impedance to DC component
• Due to this the AC component is bypassed or filtered out
• The DC component produces a voltage drop across the load resistance which is almost DC voltage

Problem : In half-wave rectification, what is the output frequency if the input frequency is 50 Hz. What is the output frequency of full wave rectifier for the same input frequency?

Solution : Half-wave rectifier –The output voltage is obtained is once in one cycle of input voltage, hence output ripple frequency after half-wave rectification = 50 Hz

Full-wave rectifier – For one cycle of input voltage, we get output twice in the same direction. Hence, the output after full wave rectification = 100 Hz

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