Light Emitting Diodes (LEDs) are semiconductors that emit light when a current is applied to them. They are comparatively much more energy efficient, when compared to lighting alternatives (E.g filament bulbs), but are generally considerably more expensive.

As with any other didode, LEDs have an anode and a cathode. However, the reverse breakdown voltage is much lower. In addition to this, a resistor is needed in series, in order to limit the rate at which current flows through the LED.

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Breadboard is used to prototype new circuits. It consists of a plastic housing with holes used to thread wire/components into. the holes are connected in lines by conductive material to adjacent holes. The diagram below shows which holes are connected to each other and how a breadboard is generally laid out (the green lines represent the conductive material).



The Basics – Volts and Amps

All circuits require an electric current to work, this is the flow of electrically charged particles. The rate at which current flows through a circuit is measured in amps.

In order for current to flow, there needs to be a potential difference between two points. This is measured in volts. If the positive terminal of a battery is 5v and the negative terminal is 0v, the potential difference is 5v. As long as the potential difference is above 0, current will flow.




A diode is a semiconductor which has two terminals: an anode and a cathode. They are composed of two layers of semiconducting material, one side doped to make it an N-type semiconductor, and the other doped to make it a P-type semiconductor. The anode is on the side of the P-type, and the cathode is on the side of the N-type.(More information about types of semiconductors can be found here: ‘https://tphelectronics.com/2016/09/30/semiconductors/‘).

One of the main characteristics of diodes is that they only allow current to flow in one direction. This means that they can be used to filter out alternating current, or even rectify it with the use of a diode bridge.



They’re used both in forward bias, and reverse bias. This refers to the direction in which current flows (forward being anode to cathode, and reverse being cathode to anode).

When forward biased no current flows through the diode until more than the minimum voltage is applied (This is because of the depletion region). This means that it can be used to filter out voltages below this value (e.g noise). The value itself is dependent on the type of diode.

When reverse biased only a few nanoamps flow through the diode.However, If the voltage applied is too large, it’ll cause the diode to breakdown. In most cases this will destroy the diode, but the breakdown in zener diodes do not destroy it (this is used to regulate voltage).