Javascripe Electronic Notebook
Basic Capacitors
by Martin E. Meserve

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Capacitors in Series

Total capacitance is calculated in the same way as resistors, except that the equations are reversed. Capacitors in parallel simply add whereas capacitors in series require a little more calculating. The resultant of two, or more, capacitors in Series can be calculated with the following equation.

With only two capacitors in series, the equation below-left can be used to determine the total capacitance. For three, or more, capacitors, the equations below-right needs to be used.

capacitor_series.gif

Two Capacitors in Series

Three or more Capacitors in Series 


           C[1] x C[2]
C[TOTAL] = -----------
           C[1] + C[2]
                         1
C[TOTAL] = ------------------------------
             1       1       1       1
           ----- + ----- + ----- + -----
           C[1]    C[2]    C[3]    C[...]

Some Quick Things To Remember About Capacitors In Series

  1. The resultant value is always less than the lowest capacitor.

  2. If the capacitors are of equal value, the resultant value is equal to the value of one of the capacitors, divided by the number of capacitors. For example, if there are three 100 pF capacitors in series the resultant value will be 100/3 = 33.333 pF.

  3. If a very large capacitor and a very small capacitor are in series, the resultant value will only be a little bit less then the smaller capacitor. For example, if there are a 10,000 pF capacitor in parallel with a 100 pF capacitor the resultant value will be 99 pF. Just 1 pF less than the lower value resistor.

Series Capacitor Calculator

Enter your capacitor values below, under C1, C2, and C3, and then click outside the box to find C Total for the capacitors in Series. If you only wish to calculate the resultant value of two capacitors, leave one of the boxes empty or enter 0.

C[1]

C[2]

C[3]

C[Total]

Note: In reference to item 3 on the left, there are many instances of having small capacitors in parallel with large ones. Most commonly, this is seen in power supplies. This is done to exploite the physical properties of the different capacitors rather than adjust the value.

Capacitors in Parallel

Capacitors in parallel are pretty straight forward, because you simply add their values together. So, in the drawing to the right, the Total Capacitance would be:

C[Total] = C[1] + C[2] + C[3] + ...

Parallel Capacitor Calculator

Enter your capacitor values below, under C[1], C[2], and C[3], and then click outside the box, to find C Total for the capacitors in Parallel. If you only wish to calculate the resultant value of two capacitors, leave one of the boxes empty or enter 0.

C[1]

C[2]

C[3]

C[Total]

capacitor_parallel.gif