Capacitors in series and parallel

Capacitors in a parallel alignment

This is the easier of the two to calculate, the total capacitance is simply the sum of both of the capacitors.

cap seriesCapacitors in parallel

Capacitors in a series alignment

When calculating capacitance in series, it’s a little more complicated. But so long as you follow the formula, it should be okay. In addition to this, you can double check your results, because it should always be lower than the value smallest capacitor in the series.

para capCapacitors in series

Passive low-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 low-pass filter

A low-pass filter, as the name suggests, allows low frequencies to pass whilst cutting off higher 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

 

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

 

Decoupling Capacitors

Capacitors block DC whilst allowing AC through. If there is noise present on a DC voltage, a capacitor can link the circuit directly to ground. The effect of this is that any noise (as AC) will filter down through the capacitor to ground, whilst DC will pass though the rest of the circuit as though the capacitor wasn’t there. When used in this way it is known as a decoupling capacitor.

coupling capacitor