Definition
A condition in which an external voltage is applied across a semiconductor PN junction in the polarity that allows current to flow easily through it. The positive terminal of the source is connected to the P-type material and the negative terminal to the N-type material, which reduces the junction's internal barrier and permits conduction.
Plain English
A diode or transistor junction is forward biased when voltage is applied in the direction that lets electricity pass through it. In this state the junction acts almost like a closed switch.
Context Anchor
Seen in aircraft electrical and electronic system discussions, especially when explaining diodes, rectifiers, alternators, and voltage regulators.
Derivation
‘Bias’ comes from the Old French ‘biais,’ meaning a slant or oblique direction. In electronics, a bias is a steady voltage that ‘leans’ a junction one way or the other. ‘Forward’ bias leans it in the direction that allows current to pass; reverse bias leans it the opposite way and blocks current.
Why Pilots Care
Proper forward bias ensures diodes and transistors function correctly in power supplies, rectifiers, and indicator circuits.
Analogy
A forward-biased diode is like a one-way valve installed in the direction the flow wants to go. In that direction, the valve opens and flow can pass.
Intuition Check
“Forward bias” does not mean a preference or opinion leaning forward. In electronics, it means the voltage is applied in the direction that allows current to flow.
Example Sentence 1
When the diode is forward biased, current flows freely from the battery through the circuit.
Example Sentence 2
In the alternator circuit, forward bias on the rectifier diodes converts AC to DC for the aircraft battery.