Fremstrøm

Fremstrøm, in electronics, is the electric current that flows through a semiconductor device when it is forward-biased, most commonly through diodes and LEDs. When a diode is forward-biased, the anode is at a higher potential than the cathode, reducing the built-in potential barrier and allowing charge carriers to cross the junction. This produces a rapid rise in current as voltage increases.

The current–voltage relationship for a forward-biased PN junction is approximately exponential, described by the diode equation I = I_s (e^{V/(nV_T)} − 1), where I_s is the saturation current, V is the forward voltage, n is an ideality factor, and V_T is the thermal voltage (about 25 mV at room temperature). In practical terms, silicon diodes show a forward voltage drop of about 0.6–0.7 volts at moderate currents, while LEDs have higher forward voltages that depend on color and material, typically ranging from roughly 1.8 to 3.3 volts.

Forward current is controlled in circuits to prevent overheating and damage, usually with a resistor or current-regulating device. Diodes specify a maximum forward current, I_f(max), and operation is sensitive to temperature. By contrast, reverse bias yields a much smaller reverse leakage current, or bakstrøm in some languages, and this current is largely independent of the forward-conduction behavior.

The concept of fremstrøm is fundamental to rectification, switching, and lighting applications, and is contrasted with bakstrøm (reverse current) in technical discussions.