Friday, December 10, 2010

SMD Capacitor

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The types of capacitor which is commonly used in small space circuit like the cellphone uses the Tantalum type of capacitor,
Tantalum capacitors are used in smaller electronic devices including portable telephones, pagers, personal computers, and automotive electronics.
It also offer smaller size and lower leakage than standard. .
There are two types of Capacitors used in Mobile Phones Circuits,
The Polarized and Non-Polarized Capacitors.
This are the Capacitors may look like  that are being used in mobile phones circuit.


SMD

The Polarized Capacitor
Tantalum Capacitors which is polarized, and may be used in DC circuits. Typical values range form 0.1uF to 470uF.
Standard Tantalum values change in multiples of 10, 22, 33, and 47. Normal Temperature Coefficient [TC] for Tantalum Capacitors is +5%.
Polarized capacitors are typically used in large voltage situations, such as DC line filtering to reduce noise related to uneven voltage levels after rectification from an AC source. Mainly measured in microfarads. Polarity is critical to these devices. They are marked with the voltage rating (usually double the circuit voltage used) as well as the farad marking.


Non-Polarized Capacitor
Non-polarized are similar to polarized except the plates are similar metal.

Polarized caps are typically used in large voltage situations, such as DC line filtering to reduce noise related to uneven voltage levels after rectification from an AC source. Mainly measured in microfarads. Polarity is critical to these devices. They are marked with the voltage rating (usually double the circuit voltage used) as well as the farad marking.

non-polarized caps are typically used in low voltage situations, both AC and DC. Polarity is not critical. Measured in pico farads typically.

Decimal multiplier prefixes are in common use to simplify and shorten the notations of quantities such as component values.
Capacitance, for example, is measured in Farads, but the Farad is far too large a unit to be of practical use in most cases. For convenience, we use sub-multiples to save a lot of figures. For example, instead of writing 0.000000000001 Farads, we write 1pF (1 picofarad).
The more common prefixes and the relationships to one another are as follows.
Abbrev.PrefixMultiply byor
ppico0.00000000000110-12
nnano0.00000000110-9
ยตmicro0.00000110-6
mmilli0.00110-3
-UNIT1100
kkilo1000103
Mmega1000000106
Units
1000 pico units=1 nano unit
1000 nano units=1 micro unit
1000 micro units=1 milli unit
1000 milli units=1 unit
1000 units=1 kilo unit
1000 kilo units=1 mega unit

Tolerance

All components differ from their marked value by some amount. Tolerance specifies the maximum allowed deviation from the specified value. Tolerances are normally expressed as a percentage of the nominal value.
For example, a component with a marked value of 100 and a tolerance of 5% could actually be any value between 5% below the marked value (95) and 5% above the marked value (105).

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