There are many different types of Capacitor. In general, they fall under one of these categories:

  1. Polarized Capacitor
  2. Non-Polarized Capacitor
  3. Variable Capacitor

Polarized capacitor types of capacitor must be connected correct way otherwise, will be damaged if connected wrongly. At least one of their leads (terminals) is mark either “+” or “−”.  Examples of these capacitors are (with brief descriptions):

Electrolytic capacitor

Electrolytic capacitors come in these two different forms; AXIAL (where the leads are built to each end) and RADIAL (where both the leads are built in the same end). Axial electrolytic capacitors stand or soldered horizontally on the circuit board while Radial upright (vertically).

Electrolytic capacitors are printed with the value of their capacitance as well as their voltage rating on them. Their negative side terminal is shades white with a mark (–) while the positive side isn’t shade or marked.

The voltage rating can be quite low and it is very important to check when selecting. If for an instance the voltage is not specify for a capacitor in a list of parts for a project, choose a capacitor with rating which is greater than the project’s power supply e.g. 25V as it is a sensible minimum for most battery circuits.

Tantalum Bead capacitors

Tantalum bead capacitors are also polarized and have low voltage ratings like electrolytic capacitors. They are used where there is  a need of a large capacitance and in a small size because they are usually small when compared to the electrolytic type.

These days, tantalum bead capacitors are printed with their capacitance, voltage rating, and polarity in full. However, older ones are colour-code used system which has two stripes (for two digits) and a spot of colour for the number of zeros to give the value in microfarad (µF).

The standard colour-code system is used just as resistor colour code, but for the spot, grey is used to mean “×0.01” and white “×0.1” so that values of less than 10µF can be shown. A third colour stripe near the leads show the voltage.

  • Yellow = 6.3V
  • Black = 10V
  • Green = 16V
  • Blue = 20V
  • Grey = 25V
  • White = 30V
  • Pink = 35V

The positive (+) lead is to the right when the spot is facing you directly.

Method of determining Tantalum Bead capacitor’s capacitance

Method of determining this type of capacitor’s capacitance value is just as using resistor colour code but, the spot colour is the multiplier. Grey spot means ×10 and White spot means ×0.1.

Examples below show capacitors colour codes and their values.

  • Blue, Grey, Black spot = 68µF
  • Blue, Grey, White spot = 6.8µF
  • Brown, Black, Brown spot = 100µF
  • Blue, Grey, Grey spot = 0.68µF
  • Red, Red, Brown spot = 220µF


These are value capacitors, these capacitors can be connected either way round. They are not damage by heat when soldering, except for one unusual type (polystyrene). They have high voltage ratings of at least 50V, usually 250V and so on. It can be difficult to find their values and they have several different labeling systems.


Many non polarized capacitors types of capacitor have their values print on them but without a multiplier, so you need knowledge of working out what the multiplier should be.

For example 0.1 means 0.1µF=100nF. Sometimes the multiplier is used in place of decimal point, for example 4n7 means 4.7nF.

Capacitor Number Code is often used on small capacitors where printing is difficult. I have also provide a table of capacitors with their number codes and capacitance in pico Farad (pF), nano Farad (nF), and micro Farad (µF) all HERE>

The stages to read them is on below

  • The 1st number is the 1st digit
  • The 2nd number is the 2nd digit
  • The 3rd number is the number of the zeros to give the capacitance in pico Farad (pF).

For example, to read the value of the capacitor below

The 1st number is 1 which is the 1st digit, 2nd number is 0 which is the 2nd digit, and the 3rd number is 4 which means 4zeros (0000)

Therefore we write; 100000pF = 100nF = 0.1µF

Some of the non-polarized capacitors have letters and voltage rating print on them. Letters on these types of capacitors indicate tolerance and sometimes company’s series.


Variable capacitors which are also one of the types of capacitor are mostly use in radio tuning circuits and sometimes called “tuning capacitors”. They have very small capacitance values, typically between 100pF and 500pF. Many of them have short spindles, which are not suitable for the standard knobs use for variable resistors and rotary switches.

Variable capacitors are not use in timing circuits because their capacitance is too small to be practical. Their range values available are very limit. Instead, timing circuits use a fixed capacitor and variable resistor if it is necessary to vary the time period.

Other types are Trimmer Capacitors.

Trimmer capacitors (trimmers) are miniature variable capacitors. They are design to be mount onto the circuit board and adjust only at the process of building the circuit.

However, the process of adjustment requires patience if adjustment is needful. Because, the presence of your hand and the tool will slightly change the capacitance of the circuit in the region of the trimmer.

Trimmer capacitors are only available with very small capacitance, normally less than 100pF. It is impossible to reduce their capacitance to zero, so they are usually specified by their minimum and maximum values, for example 2 – 10pF. Trimmers are the capacitors equivalent of preset which are miniature variable resistors.



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