Framåtfallsspänning

Framåtfallsspänning refers to the voltage drop that occurs across a semiconductor junction, such as a diode or a transistor, when it is forward-biased. This forward-biasing condition means that a positive voltage is applied to the anode and a negative voltage to the cathode in a diode, or similar polarities for transistor terminals. The forward-bias pushes charge carriers (electrons and holes) towards the junction, allowing current to flow.

The framåtfallsspänning is not a fixed value but depends on the type of semiconductor material and the specific device. For silicon-based diodes, this voltage is typically around 0.6 to 0.7 volts. For germanium diodes, it is lower, around 0.2 to 0.3 volts. Light-emitting diodes (LEDs) have a higher framåtfallsspänning, which varies with the color of the light emitted, ranging from approximately 1.5 volts for red LEDs to over 3 volts for blue or white LEDs.

This voltage drop is essentially the minimum voltage required to overcome the potential barrier at the semiconductor junction and allow significant current conduction. Once this threshold voltage is reached, the current through the device increases rapidly with a small increase in applied voltage. The framåtfallsspänning is an important parameter in electronic circuit design, affecting how components behave and how much power they dissipate. It is also a characteristic that distinguishes different types of diodes and is crucial for understanding their operation.