HO 11 Capacitors and identification

8/7/2019 HO 11 Capacitors and identification

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File: Capacitors and identification.doc

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Capacitors

Types of Capacitors

1. Paper and plastic Capacitors use a variety of dielectric materials. Some of theseinclude Mylar, polystyrene and polyethylene for the plastic types, and waxed or oiled

paper for the older, less expensive paper type. Typically, the plates are long strips oftinfoil separated by the dielectric material. The foil and the dielectric material are

commonly rolled into a cylindrical component, It is interesting to note that because oftheir construction, each plate has two active surfaces. This means to calculate the

plate areas, use twice the area of one plate, rather than only the area of one plate.

Typical capacitance values for this type capacitor range from about 0.001 uF to 1 uF

or more. Paper and plastic capacitors are typically used in fairly low-frequencyapplications such as audio amplifiers.

2. Mica Capacitors use mica for the dielectric material. Because the mica dielectric hasa high breakdown voltage, these low-capacitance, high-voltage capacitors are

frequently found in high-voltage circuits. Often, their construction is alternate layersof foil with mica that is molded into a plastic case. They are compact, moisture-proof,

and durable. Voltage ratings are in thousands of volts. Typical capacitance values

range from about 5 to 50,000 Pico farads, depending on voltage ratings.

3. Ceramic Capacitors are typified by their small size and high-dielectric strength.Ceramic capacitors generally come in the shape of a flat disk (disk ceramics), orcylindrical shapes. These capacitors are also compact, moisture-proof, and durable.

Typical available ranges having 1,000 V ratings are from approximately 5 pF to about

5,000 pF. At lower voltage ratings, higher capacitance values are available. Becauseof good dielectric characteristics, both mica and ceramic capacitors can be used in

applications from the audio-frequency range up to several hundred megahertz.

4. Electrolytic Capacitors have several prominent characteristics, including:a. High capacitance-to-size ratio;b. Polarity sensitivity and terminals marked + and -;c. Allow more leakage current than other types; andd. Have their C value and voltage rating printed on them.

The main advantage of the electrolytic capacitor is the large capacitance-per-sizefactor. Two obvious disadvantages are the polarity, which must be observed, and the

higher leakage current feature. Also, in many capacitors of this type, the electrolyte

can dry out with age and depreciate the capacitor quality or render it useless. Becauseof the losses of the dielectric at higher frequencies, electrolytic capacitor applications

are generally limited to power-supply circuits and audio-frequency applications.


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5. Tantalum capacitors are in the electrolytic capacitor family. The use tantaluminstead of aluminum. One important quality of tantalum capacitors is they providevery high capacities in small-sized capacitors. They have lower leakage current than

the older electrolytics. Also, they do not dry out as fast, thus have a longer shelf life.

Because they are generally only manufactured with low-voltage ratings, they are used

in low-voltage semiconductor circuitry. Tantalum capacitors are expensive.

6. Chip (SMT) capacitors are very small in size; these devices are primarily used ascompact components on PC board-type circuitry where space is at a premium. Also,

the construction style, with virtually no lead length, enables these components to have

minimal stray inductance or capacitance. This makes them useful in high frequencyapplications. Materials commonly used in the construction of these devices include

layers of conductive material, using ceramic as the dielectric between layers. Their

miniature size makes marking their value difficult. Therefore, they are typicallymarked with a short two-character code (which you may need a magnifying glass to

read). This two-letter code consists of a letter, which indicates the significant digits inits value, and a number, which indicates the multiplier (or how many zeroes should

follow the significant digits). This coding indicates the capacitor value in PF.

TYPICAL RANGE OF RATINGS FOR VARIOUS CAPACITORS

(Shown in standard electronic parts catalogs)

CAPACITOR

TYPE

CAPACITANCE

RATING

VOLTAGE

RATINGS

TOLERANCE

RATINGS

OPERATIONAL

TEMPERATURE

TEMPERATURE

COEFFICENTS

Paper 0.001-1.0 uF 100-1,500V

+/- 10%

(common)

-40 to +85C N/A

Mica 5-50,000 pF 600 toseveral kV

+/- 1-5% -55 to + 125C N/A

Ceramic 1-10,000 pF 1kV 6 kV +/- 10-20% -55 to +85C N or P0-750

Electrolytic 10-1,000 uF 5-500V -10-50% -40 to +85C N/A

NOTE: Temperature coeffecient ratings are generally given for ceramic-type capacitorstht are designed to increase or decrease in capacitance with temperature change. The

rating is normally given in parts-per-million per degree Celsius. For example, if a

capacitor decreases 500 ppm per degree Celsius, it would be labeled N500.


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Ceramic Capacitors

1st

digit

2nd

digit

Multiplier

Tolerance

Decimal Pt. 2nd

digit

203M 221K 1st

digit 5R6D Tolerance

20,000 pF 220 pF 5.6pFor +/- 10% +/- 0.5 pF

0.02 uF +/- 20%

Third-Digit Multiplier Letter Tolerance Code Letter Tolerance Code Number Multiply by Under 10 pF values: Over 10 pF values:

0..1 Letter Tolerance Letter Tolerance1..10 B.+/- 0.1pF E...+/- 25%

2..100 C.+/- 0.25pF F...+/- 1%3..1000 D.+/- 0.5 pF G...+/- 2%

4..10,000 F.+/- 1.0 pF H...+/- 2.5%

J....+/- 5%K...+/- 10%

M...+/- 20%

P ..-0%, +100%

S ..-20%, +50%W..-0%, +200%

X ..-20%, +40%

Z ..-20%,+80%


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Surface Mount Technology (SMT) Capacitor Coding

SMT Capacitor Significant Figures Letter Code SMT Capacitor Multiplier Code

Character Significant

Figure

Character Significant

Figure

Number Decimal

MultiplierA 1.0 R 4.3 0 1

B 1.1 S 4.7 1 10

C 1.2 T 5.1 2 100

D 1.3 U 5.6 3 1,000

E 1.5 V 6.2 4 10,000

F 1.6 W 6.8 5 100,000

G 1.8 X 7.5 6 1,000,000

H 2.0 Y 8.2 7 10,000,000

J 2.2 Z 9.1 8 100,000,000

K 2.4 a 2.5 9 0.1

L 2.7 b 3.5M 3.0 d 4.0

N 3.3 e 4.5

P 3.6 f 5.0

Q 3.9 m 6.0

n 7.0

t 8.0

y 9.0

Decoding Examples:

(C = 1.2) (Y = 8.2)

(3 = X 1,000) (2 = X 100)

C3 Y2 39

1,200 pF 820 pF 39 pF

(Letter plus number = above 100 pF) (Numbers only = below 100 pF)

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HO 11 Capacitors and identification