The resistance of a reverse diode is very high.
A diode is a semiconductor device that allows current to flow in one direction (forward bias) and blocks current flow in the opposite direction (reverse bias). In reverse bias, the diode acts as an insulator, offering a very high resistance.
Understanding Reverse Bias
In reverse bias, the positive terminal of the voltage source is connected to the cathode (negative) side of the diode, and the negative terminal is connected to the anode (positive) side. This creates a depletion region within the diode, which acts as a barrier to current flow.
Factors Affecting Reverse Resistance
The resistance of a diode in reverse bias is not constant but is affected by several factors, including:
- Voltage: The higher the reverse voltage applied, the lower the reverse resistance, until the diode breaks down.
- Temperature: The reverse resistance decreases with increasing temperature.
- Diode type: Different types of diodes have different reverse resistance characteristics.
Practical Implications
The high reverse resistance of a diode is crucial for its operation in various applications. For example, in rectifier circuits, diodes are used to convert AC voltage to DC voltage. During the negative half-cycle of the AC input, the diode is reverse-biased, and its high resistance prevents current flow. This ensures that only the positive half-cycle of the AC voltage is passed through the diode.
Example
Consider a silicon diode with a reverse breakdown voltage of 50V. If a reverse voltage of 10V is applied, the diode will exhibit a very high resistance, effectively blocking current flow. However, if the reverse voltage is increased to 60V, the diode will enter breakdown, and the resistance will drop significantly, allowing large currents to flow.
