Passive high-pass filter

‘Passive’ refers to the fact that this type of filter is incapable of power gain and uses no active components. This also means that no external power source is needed for it to function.

Passive high-pass filter

A high-pass filter, as the name suggests, allows high frequencies to pass whilst cutting off lower frequencies. The cut-off frequency (Fc), is calculated by using the formula below. ‘R’ is the resistor value, and ‘C’ is the capacitor value.

Frequency cut-off formula



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.

led (1)


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).