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Capacitor Dielectric Properties

The question arises all the time concerning which capacitor type to use for a particular application. This table provides a guideline for starters, but is in no way exhaustive. (DA = dielectric absorption)

The unofficial temperature coefficient designations for the capacitors are as follows: The temperature coefficient is given as "P" for positive, "N" for negative, followed by a 3-digit value of the temperature coefficient in ppm/°C. For example "N220", is -200 ppm/°C, and "P100" is +100 ppm/°C. The one exception in this system is "NPO" where an "O" instead of "0" is used, but quite a number of people use "NP0." In any event "NPO" means stable with temperature.







Dielectric Type DA Advantages Disadvantages Uses
NPO Ceramic
(COG)
<0.1% Tight tolerance
High Q factor, low K
Small case size
Inexpensive
Good stability
Wide range of values
Low inductance
DA generally low, but may not be specified
Limited to small values (10 nF)
Low loss, timing and tuning applications
Monolithic Ceramic
(High K)
>0.2% Low inductance
Wide range of values
Poor stability
Poor DA
High voltage coefficient
 
X7R  (BX)
(Barium Titanate)
  Inexpensive
Low DA available
Wide range of values
Smaller case size
Damaged by temperature
    >+85° C
Loose tolerances
High inductance
Bypassing, coupling, and frequency discrimination circuits
Z5U & Y5V   Smallest case size
Very large values
Damaged by voltages
    >25 WVDC
Very loose tolerances
Bypassing and coupling
Polystyrene 0.001%
to 0.02%
Inexpensive
Low DA available
Wide range of values
Good stability
Damaged by temperature
    >+85° C
Large case size
High inductance
Timers and filters
Polypropylene 0.001%
to 0.02%
Inexpensive
Low DA available
High dielectric strength
Wide range of values
Negative TC
Damaged by temperature
    >+105° C
Large case size
High inductance
Stable oscillators and filters, sample and hold circuits and pulse handling circuits
Teflon 0.003%
to 0.02%
Low DA available
Excellent stability
Operational >+125° C
Wide range of values
Relatively expensive
Large size
High inductance
Timing and pulse shaping circuits
MOS 0.01% Good DA
Small
Operational above +125° C
Low inductance
Limited availability
Available only in small capacitance values
 
Polycarbonate 0.1% Good long-term stability
Low cost
Wide temperature range
Large size
DA limits to 8-bit applications
High inductance
Timers, filters and applications in high ambient temperature
Polyester 0.3%
to 0.5%
Moderate stability
Low cost
Wide temperature range
Low inductance (stacked film)
Self-healing
Large size
DA limits to 8-bit applications
High inductance
Bypassing and coupling
Mica >0.003% Low loss at HF
Low inductance
Very stable
Available in 1% values or better
Quite large
Low values (<10 nF)
Expensive
 
Aluminum Electrolytic High Large values
High currents
High voltages
Small size
High leakage
Usually polarized
Poor stability
Poor accuracy
Inductive
 
Tantalum Electrolytic High Small size
Large values
Medium inductance
High melting point
High dielectric strength
Good ductility
Quite high leakage
Usually polarized
Expensive
Expensive
Poor stability
Poor accuracy
 


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