Question

What is forward and reverse current?

Answer 1

Forward Bias Current

1. Reverse bias is when the p-side of the diode is connected to the negative voltage of the battery and the n-side is connected to the positive voltage of the battery.
2. This causes an increase in the thickness of the depletion layer. This allows very less current to flow through the PN junction
3. The current that flows in the forward direction when the diode is forward biased is called forward current.
4. Forward current is a diffusion current because this current is passing through the junction from higher concentration to lower concentration.

Reverse bias current

1. Reverse bias is when the p-side of the diode is connected to the negative voltage of the battery and the n-side is connected to the positive voltage of the battery.
2. This causes an increase in the thickness of the depletion layer.
3. This allows very less current to flow through the PN junction.
4. The current that flows in the reverse direction when the diode is reverse bias is called Reverse current.
5. The reverse current is designed to be smaller than the forward current.

1. The graph is drawn for voltage and current for forward and reverse bias.
2. When a diode is forward biased it conducts current (IF) in forward direction. The value of IF is directly dependent on the amount of forward voltage.
3. Forward Voltage is measured across the diode and Forward Current is a measure of current through the diode.
4. When the forward voltage across the diode equals 0V, forward current (IF) equals 0 mA.
5. When the value starts from the starting point (0) of the graph, if $V_f$ is progressively increased in 0.1-V steps, IF begins to rise.
6. When the value of $V_f$ is large enough to overcome the barrier potential of the P-N junction, a considerable increase in IF occurs. The point at which this occurs is often called the knee voltage.
7. The vertical reverse current line in this graph has current values expressed in microamperes.
8. The amount of minority current carriers that take part in conduction of reverse current is quite small. In general, this means that reverse current remains constant over a large part of reverse voltage.
9. When the reverse voltage of a diode is increased from the start, there is a very slight change in the reverse current. At the breakdown voltage (VBR) point, current increases very rapidly. The voltage across the diode remains reasonably constant at this time.
10. This constant-voltage characteristic leads to a number of applications of diode under reverse bias condition. The processes which are responsible for current conduction in a reverse-biased diode are called as Avalanche breakdown and Zener breakdown.