vastajännitteisiä

Vastajännitteisiä is a Finnish term that translates to "reverse biased" in English, commonly used in electronics. It describes a situation where a voltage is applied across a semiconductor junction, such as a diode, in a direction that opposes the normal flow of current. In a p-n junction, for instance, reverse bias occurs when the positive terminal of the voltage source is connected to the p-type material and the negative terminal to the n-type material.

When a diode is reverse biased, a depletion region forms and widens. This region is devoid of free charge carriers, acting as an insulator and preventing significant current from flowing through the device. A very small leakage current, known as reverse saturation current, may still flow, but it is typically negligible for most applications. If the reverse bias voltage exceeds a certain limit, known as the breakdown voltage, the diode will conduct current heavily, potentially leading to damage. This breakdown can occur through mechanisms like Zener breakdown or avalanche breakdown. In some specialized diodes, like Zener diodes, the breakdown is designed to be a controlled and predictable event, allowing them to be used for voltage regulation.