QS Study

When a voltage is applied across a diode in such a way that the diode allows current, the diode is said to be forward-biased. It is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. For example, a silicon diode will conduct current only if its anode is at a positive voltage compared to its cathode; it is then said to be forward biased.

Characteristics of Forward Biasing

  1. Inside the junction diode, current flow is by both majority carriers; but in an external circuit, current flow is by electrons only.
  2. Current flow in forward bias of the order of flow mA.
  3. If the applied voltage is increased temperature also increases.
  4. The graph of the current versus applied voltage does not give a straight line.
  5. The width of the depletion region of the diode progressively decreases with forwarding biasing.

The voltage potential is connected positive, (+ve) to the P-type material and negative, (-ve) to the N-type material across the diode which has the effect of Decreasing the PN junction diodes width.

When the junction is in forward bias, then charge carriers diffuse from majority region to the minority region – electrons diffuse toward holes. So, holes and electrons combine near the depletion region. As a result, the depletion region starts reducing and above knee voltage, it disappears.

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