A diode is used as a switch because its behavior changes dramatically based on the voltage applied to it, effectively acting as either an open or closed circuit. The change of forward and reverse biased states makes the diode work as a switch, the forward being ON and the reverse being OFF state. (24-Sept-2021)
Diode Operation as a Switch:
Diodes function as switches due to the properties of the PN junction. Here's a breakdown:
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Forward Bias (ON State):
- When a positive voltage (greater than the forward voltage) is applied to the anode (P-side) and a negative voltage to the cathode (N-side), the diode is forward biased.
- In this state, the diode allows current to flow easily, behaving like a closed switch or a short circuit.
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Reverse Bias (OFF State):
- When a negative voltage is applied to the anode and a positive voltage to the cathode, the diode is reverse biased.
- In this state, the diode blocks current flow, behaving like an open switch or an open circuit.
- Only a very small leakage current flows in this state.
Summarizing Diode Switching Action in a Table:
| Bias Condition | Voltage Polarity (Anode vs. Cathode) | Current Flow | Switch Equivalent | State |
|---|---|---|---|---|
| Forward Bias | Positive > Cathode | High | Closed Switch | ON |
| Reverse Bias | Positive < Cathode | Very Low | Open Switch | OFF |
Practical Implications:
- Diodes are commonly used in circuits where current needs to flow in only one direction.
- Rectifiers, which convert AC to DC, are a prime example of diodes acting as switches.
- Signal detection and wave shaping circuits also utilize the switching behavior of diodes.
