Bredhurst Receiving and Transmitting Society

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For those who want to relate the current flow to electorn flow then here is an explaination.

The circuit diagram for a diode is :-

This component is part of a group of components that use the special properties of materials called "semiconductor" to control the flow of electrons (others in the group are transistors, mosfets and leds). The diode is made up of two special semiconductor materials called P and N type conductors. In a diode they are arranges as shown below with the P type in the place of the arrow and the N in place of the bar on the circuit diagram.

This concept of P and N type semiconductor materials will be used again in the transistor section further on.

The diode only allows a flow of electrons in one direction and thus a current will only flow in one direction. As you learned in the foundation Course the conventional current flow, or just current flow, is in the direction of the arrow ( but in actual fact the electrons would be flowing the opposite way).

If this is confusing then think only in terms of what we have called converntional current flow and that is in the direction of the arrow head so the arrow head would be positive and this is shown in the diagram below.

As you never obtain something for nothing, for the action of the diode to take place there is a need for a small forward potential (also called forward bias or turn on voltage) to "turn" the diode on. What this means in real terms is say there is a 12V potential prior to the diode then afterwards there would be of the order of 11.4V, 0.6V being the "forward potential".