Capacitors in Series and Parallel

This post explains how to calculate the value of the overall capacitance of more than one capacitor, both in series and in parallel.

Capacitors have limited application in digital circuits, including those we might use in conjunction with either a Raspberry Pi or some variety of microcontroller.

But you will find them as the second component in a classic RC timing circuit, where a capacitor is charged through a resistor, to produce some kind of event after a predictable length of time, or in decoupling noise (ripple) to ground.

Where capacitors are also often used is in a DC blocking application. To couple AC, such as audio or radio frequency into the next stage of a circuit, but block the DC from the previous stage.

Capacitors in Series

The way to calculate the overall capacitance of two or more capacitors placed in series, is the same as the calculation for resistors in parallel.

Here is a text-friendly writing of it. Sighted readers please note, the format of this explanation of the calculation is to make it readable with a screen reader. The calculation is spread over three items in a list. Assuming two capacitors:

  • C1 x C2
  • over
  • C1 + C2

If all of the capacitors are of the same value, then the value of one divided by the number of capacitors is the easiest way to make this calculation.

Capacitors in Parallel

The overall capacitance of a number of capacitors in parallel is very easy to calculate.

If you place more than one capacitor in parallel, the overall capacitance value of that circuit is simply the sum of all of the capacitors.

For example, given two capacitors:

  • C1 = 100µF (100 micro Farads)
  • C2 200µF (200 micro Farads)

The value is simply:

  • C1 + C2, or 300µF (micro Farads)

If you put two capacitors in parallel, then the values when you add them together must be in the same unit.