Utarmningsspänning

Utarmningsspänning, or depletion voltage in English, is a term used in semiconductor physics. It refers to the voltage at which a junction, such as a p-n junction, becomes fully depleted of mobile charge carriers. This depletion occurs when an external voltage is applied in the reverse-bias direction.

In a p-n junction, mobile charge carriers, which are holes in the p-type material and electrons in the n-type material, naturally diffuse across the junction, creating a depletion region where there are very few free charge carriers. When a reverse bias voltage is applied, it further increases the width of this depletion region by pulling the mobile charge carriers away from the junction.

The utarmningsspänning is the specific reverse-bias voltage that causes the depletion region to extend across the entire junction or a significant portion of it, effectively preventing current flow due to the lack of mobile carriers. Beyond this voltage, any further increase in reverse bias will have little effect on the current, which will remain very small (leakage current).

This concept is crucial in understanding the behavior of diodes, transistors, and other semiconductor devices. The breakdown voltage of a diode, for instance, is related to the utarmningsspänning, though breakdown occurs when a sufficiently high reverse voltage causes a sudden increase in current, often due to mechanisms like Zener breakdown or avalanche breakdown.