Takajännitteellä

Takajännitteellä, often translated as "reverse bias" in English, refers to a condition in semiconductor devices, particularly diodes and transistors, where the voltage applied across the device is in the opposite direction to that which allows current to flow. For a standard p-n junction diode, takajännitteellä occurs when the positive terminal of a voltage source is connected to the n-type semiconductor material and the negative terminal is connected to the p-type semiconductor material.

In this configuration, the applied voltage causes the depletion region, a region devoid of free charge carriers at the junction, to widen. This widening increases the resistance across the junction, effectively preventing the flow of significant current. The current that does flow under takajännitteellä is typically very small and is known as leakage current, primarily due to minority carriers.

The behavior of a device under takajännitteellä is crucial for its operation in many electronic circuits. For example, in rectifier circuits, diodes are used to allow current to flow in one direction (forward bias) while blocking it in the other (reverse bias). Transistors also exhibit different behaviors in their different regions of operation, which are influenced by the voltage conditions, including those that can be considered analogous to takajännitteellä for their internal junctions. Exceeding the breakdown voltage under takajännitteellä can lead to a rapid increase in current, potentially damaging the device, although some devices are designed to operate in this breakdown region.