The purpose of a diode is to allow current to flow easily in one direction, anode to cathode, while blocking current flow in the opposite direction, cathode to anode. This is accomplished through the use of P-type and N-type semiconductor materials. In their normal state, they create an electron depletion region at the junction of the two materials. In order to actually get the electrons to flow across the semiconductor — to collapse the depletion region — you must have a certain amount of voltage to press the current across. That is called the “diode forward voltage”, or sometimes the “voltage drop”. Below that voltage, you don’t have enough electrical potential energy to get the electrons across the semiconductor junction. Above it, electrons start to flow quite easily. The diode is considered forward biased when current is easily able to flow from the anode to the cathode.
Here are some example components…
|1N4007 Rectifier Diode||Diode Forward Voltage 1.1V|
|LTST-C190KRKT LED||Diode Forward Voltage 2.7V|
|MBRA340T3G Schottky Diode||Diode Forward Voltage 0.390V|
For more about diodes, check out the video below by [Bil Herd], part of the Hackaday crew: