Forward and reverse bias refer to the two basic operating conditions of a semiconductor diode, such as a PN junction diode. In forward bias, the diode is connected in such a way that the positive terminal of the voltage source is connected to the P-type material (anode) and the negative terminal to the N-type material (cathode). This configuration allows current to flow easily through the diode, as the applied voltage reduces the potential barrier between the P and N regions, enabling majority carriers (electrons in the N-region and holes in the P-region) to move across the junction.
Conversely, in reverse bias, the diode is connected with the positive terminal of the voltage source to the N-type material (cathode) and the negative terminal to the P-type material (anode). This arrangement increases the potential barrier at the junction, preventing majority carriers from crossing the junction easily. As a result, only a small leakage current (due to minority carriers) flows through the diode in reverse bias, and the diode acts as an insulator.
A diode is forward biased when it is biased in a way that allows current to flow through it easily. This means the diode is connected in such a manner that the voltage applied across it reduces the depletion layer’s width, allowing current to pass through due to majority carrier movement.
Biasing refers to the application of a DC voltage to establish a specific operating condition for electronic components such as diodes and transistors. For diodes, biasing determines whether the diode operates in forward bias (conducting state) or reverse bias (non-conducting or blocking state). Proper biasing is crucial for ensuring that electronic circuits function correctly and efficiently.
A PN diode, or simply a diode, consists of a PN junction formed by doping semiconductor material with P-type (positively charged) and N-type (negatively charged) impurities. This creates a region where electrons (majority carriers in N-type) and holes (majority carriers in P-type) combine to form a depletion zone or region devoid of mobile charge carriers when no external voltage is applied. When a forward bias is applied, the diode conducts current easily due to reduced depletion layer width, while reverse bias prevents significant current flow except for a small leakage current.