| Capacitors |
| Capacitors are devices that hold a charge of electricity. The unit of capacitance is the Farad. Though we are beginning to see capacitors above one Farad, we normally see them in smaller sub units, called microfarads and picofarads. There are several types of capacitors, each useful for a different purpose. Some of the more commonly used types are ELECTROLYTIC (used most often for power supply filtering and other low frequency bypass purposes), TANTALUM (a special type of ELECTROLYTIC capacitor), CERAMIC (common in high frequency bypass circuits), MICA (still widely used in RF circuitry) and PAPER (used when a medium high capacity is needed but use of an ELECTROLYTIC is not desirable). Electrolytic and tantalum capacitors are normally POLARIZED, this means that they have a positive and negative terminal. Most other types are NON-POLARIZED, though some paper capacitors are also polarized. The banded end of a paper capacitor generally shows the connection to the outside foil layer of the capacitor, which is generally connected to the lower voltage or ground side of the circuit. Most ceramic or disc capacitors now carry what many feel are cryptic markings, such as 104 or 472. I will list here a chart of how to read these markings. 104 = .1 mfd. 224 = .22 mfd 334 = .33 mfd 103 = .01 mfd 223 = .022 mfd 333 = .033 mfd 102 = .001 mfd 222 = .0022 mfd 332 = .0033 mfd 101 = .0001 mfd 221 = .00022 mfd 331 = .00033 mfd 100 = .00001 mfd or 100 pf. Other values are similarly read, (i.e. 472 = .0047 mfd) Most very small value capacitors (less than 100 pfd) are labeled directly with the value of the capacitor. |
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