Diodes are the simplest of electronic devices. At their most basic, they are like one-way valves for electrical current, but they can be used for so many different things. Common applications include voltage rectification, voltage regulation, circuit protection, current control, and even simple (but inefficient) logic circuits. On this page you will find videos on

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PN Junctions

The way that electrons flow in doped semiconductors is very interesting, but the really interesting effects occur when you have p-type semiconductor and an n-type semiconductor created side by side to create a PN junction. The properties of the PN junction make it useful for several important electronic devices. The most basic such device is the diode which is simply a PN junction with leads on it to allow it to be used in a circuit.

Modelling Diodes

When you have a diode in a circuit, you will often want to predict its behaviour, or conversely, you want a certain behaviour in  ac circuit and want to ensure the diode will exhibit that behaviour. Diode modelling is the process of creating a mathematical or behavioural model of the diode that helps you to predict how the circuit will behave (electrically speaking) with the diode in it. Depending on the level of precision you want in your model, there are different models that you can choose from. This video describes several different models that you can use for diodes

Diode Model Examples

In case just knowing the theory behind modeling diodes is not enough, this video looks at a few simple examples and analyzes circuits using different diode models. The forward bias models used are:

  1. Diode is a short
  2. Diode has a small voltage drop
  3. Diode has a small voltage drop and a resistance
  4. Diode follows Shockley’s Diode Equation

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Half Wave Rectifiers

Half wave rectifiers can be created using a single diode in an AC circuit. Since diodes only allow current to pass in one direction, they will only allow current to flow during half of an AC circuit. Half wave rectifiers cut off half of the signal and this video shows how they work:

Full Wave Bridge Rectifiers

Full-wave rectifiers force AC current to flow through a circuit in one direction by using a clever configuration of diodes. Full-wave bridge rectifiers fulfill a very important stage in AC-DC conversion.