Capacitors 1: Description

by gaussmarkov

Appearance

mylar capacitors

There are many kinds of capacitors and several popular ones are pictured here. Generally, capacitors have two leads. Some are axial leaded, like resistors, and others are radial leaded, with both leads at one end. Stompbox layouts seem to use radial leaded capacitors most often, but axial leaded are just as good. Unlike resistors, some capacitors are polarized, with positive and negative leads: the voltage across such capacitors must agree with the polarity of the leads. Take care to orient polarized capacitors correctly in a circuit.

mylar capacitors
Generally, polarized capacitors have lead markings on the casing, like a colored band of minus (negative) signs. The radial electrolytic capacitor pictured above has a black casing with a gray band and you can just see one minus sign. Note also that the negative lead is shorter than the positive lead. On axial electrolytic capacitors, arrows often point toward the negative lead. The blue capacitor shown here is an example. When the arrows are not present, note that the aluminum can (housing) shows on the negative end while the positive end has a (black) seal insulated from the housing. Often, the indentation or groove around one end of the casing is on the positive end. You can also see some of these features on the blue capacitor below.

mylar capacitors

mylar capacitors

mylar capacitors

The other capacitors pictured are mylar film (the brown and green ones above), box film (yellow), and ceramic disc (light brown).

There are many types of capacitors because there are many ways to make them and each has its advantages. There are accompanying disadvantages of course. For stompboxes, important considerations are size and effects on an audio signal. There is a lot of discussion about the latter, with many different views. I offer my interpretation of good advice for beginners below under Values.

Symbols

capacitor schem

There are also a variety of schematic symbols for capacitors. Two popular symbols are shown here, one for non-polarized and one for polarized capacitors. Often, the non-polarized symbol is made into a polarized symbol by adding a plus sign to show polarity. The polarized symbol shown here does not always have its polarity marked, but the curved side is always the negative lead. There is a nice table of other capacitor schematic symbols on the Capacitor page of Wikipedia.

Capacitors are labelled with the capital letter C and a number, like C2. In the Fuzz Face schematic described in Eagle 1: Description, C1 is a polarized capacitor with its positive lead on the input. C2 is another polarized capacitor, positive lead going to ground. C3 is non-polarized. This circuit has a positive ground (note that the voltage supply has a negative symbol) and this explains the orientation of the polarized capacitors. In a negative ground circuit, they would be reversed.

[image: Basic Fuzz Face schematic]

capacitor board The layout symbols for capacitors are ovals, boxes, circles, and the schematic symbol.

Values

Capacitor values are called capacitance, which is measured in farad units that are denoted by the capital letter F. In stompbox circuits, the largest capacitances are on the order of 10-6 farads and their units are microfarads, denoted by μF. For typing convenience,

μF and uF and mF

are equivalent, where u has a similar appearance to μ and m is the Latin character that corresponds to μ. (The mF notation is awkward because m often denotes “milli” or “one-thousandth” as in mA for milliamps or mm for millimeter. Nevertheless you will see it occasionally, as in the Small Bear catalog.) The smallest capacitances one sees are picofarads or 10-12 farads, denoted pF. In between, there are nanofarads (10-9 farads denoted nF). Many schematics avoid nF, writing .01μF instead of 10nF. If there are no units for the capacitors on a stompbox schematic, one generally assumes that the units are μF.

Although the notation is usually reserved for resistors, one occasionally sees the decimal point in a capacitor value replaced with the capacitor’s magnitude. For example, 2.2nF is sometimes noted as 2n2. Also the F (for farad) is also frequently dropped even when there is a decimal point: 2.2n instead of 2.2nF.

Tolerances are generally ±20%, much less accurate than common resistors. As a result, capacitors generally come in fewer values than resistors, but the values are organized in the same way. Capacitance values proportional to 10, 15, 22, 33, 47, and 68 are quite common. See the Values section of Resistors 1: Description for additional information or this Wikipedia entry.

  • ceramic: often used for small capacitances in the 1pF to 1000pF range.
  • polarized electrolytic: typically appear in power supply filters with values 10μF and higher.
  • film: come in various kinds and their values cover a large range, say 1,000pF to several μF.
  • mica: used for small capacitances like ceramic capacitors.
  • tantalum: polarized and used in the signal path for their character. For examples, see the schematic of the tubescreamer clone or the schematic of the Red Llama clone.

Ratings

Capacitors are rated for the voltage potential across their leads. 16V are typically used for 9V stompbox circuits. Move up to 25V for an 18V power supply. Many builders just buy 25V capacitors because they can be used in either case. Some capacitor values are not available without moving up to higher voltage ratings like 50V. There is no apparent problem with using such higher voltage ratings in stompbox circuits.

Further Information

The Wikipedia has (at least) two helpful pages for general reference: Capacitor and Capacitor (component).

To learn more about types of capacitors and their audio properties, read “the Cap FAQ on muzique.com”. There is much discussion about the special character of certain capacitors and Aron’s stompbox forum is a good place to get a sampling.


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13 Responses to “Capacitors 1: Description”

  1. Electronics-Lab.com Blog » Blog Archive » [Basic Electronics] – Capacitors Tutorial said:

    […] Capacitors 1: Description […]

    Posted 01.02.2008 at 1:53 am

  2. jd said:

    no mention of what a capacitor IS or DOES!

    Posted 01.06.2008 at 7:37 pm

  3. gaussmarkov said:

    jd,

    exactly. 😉

    i agree that the beginner is interested in what a capacitor does, but this page covers more immediate concerns for soldering up the first circuit (like what “mF” means).

    if you keep reading through the capacitor posts, you will find answers to the IS and DOES questions. 😀

    cheers, paul

    Posted 02.06.2008 at 5:14 am

  4. gharie said:

    i like to know the units and quantities of capacitor!
    tnk you!

    Posted 11.08.2008 at 7:52 pm

  5. Jhong said:

    Do you have some discription of 1200mfd capacitor?? tnx

    Posted 11.12.2008 at 7:32 pm

  6. Capacitors 1: Description said:

    […] Article as been written by gaussmarkov You can check the original herehere Posted by […]

    Posted 07.09.2009 at 10:47 pm

  7. vinni said:

    i have 2E104k capacitor i just want to know what is the function of the capacitor.
    thankyou

    Posted 10.07.2010 at 2:35 pm

  8. william f. pabalan said:

    do you know the exact symbol of ceramic and mylar capacitor?

    Posted 15.07.2010 at 5:44 am

  9. Redhuan Jamil said:

    if i put regular capacitor at where the polarized one should be , what will happen?
    will the circuit run nicely ?

    Posted 06.01.2011 at 1:50 am

  10. gaussmarkov said:

    You can substitute a nonpolarized capacitor for a polarized one with the same value and voltage rating and the circuit will still work. It will not necessarily sound the same.

    Posted 08.01.2011 at 7:24 am

  11. srishti said:

    how can we check the value of light brown coloured capacitor using colour coding??

    Posted 15.05.2012 at 6:39 am

  12. srishti said:

    how do we use capacitor on breadboard?

    Posted 15.05.2012 at 6:41 am

  13. Jean-Robert Herard said:

    I need 2 capacitors of 50 microfarads.

    Posted 05.05.2013 at 5:07 pm