[SI-LIST] Re: SMD capacitor question

  • From: John Barnes <jrbarnes@xxxxxxxxx>
  • To: rvfm80@xxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
  • Date: Fri, 30 Jan 2004 14:34:26 -0500

Robert,
Class I ceramic capacitors are classified as ultra-stable, and are a
good choice for loop filters.  They are usually made from titanium
dioxide or neodymium oxide, so they don't exhibit the piezoelectric
effect, with:
*  Relative permittivity of 6 to 500.
*  Linear temperature coefficient of capacitance (TCC, can be as low as 
   30 parts per million per degree Celsius).
*  Little effect on capacitance from voltage, frequency, or time.
*  Little effect on dissipation factor from voltage, frequency, or time.

The last three characters of the capacitor designation specify the TCC
as follows:

Significant     Multiplier for TCC,     Tolerance of TCC, 
Digits of TCC   in 1/°C                 in 1/°C

A = 0.9         0 = -0.000001           G = ±0.000030 
B = 0.3         1 = -0.000010           H = ±0.000060 
C = 0.0         2 = -0.000100           J = ±0.000120 
M = 1.0         3 = -0.001000           K = ±0.000250 
P = 1.5         4 = -0.010000           L = ±0.000500 
R = 2.2         5 = 0.000001            M = ±0.001000 
S = 3.3         6 = 0.000010            N = ±0.002500 
T = 4.7         7 = 0.000100    
U = 7.5         8 = 0.001000    
                9 = 0.010000    

The above information is taken from chapter 8, Capacitors, of my book
Robust Electronic Design Reference Book, Volume 1, which should be in
print fairly soon now from Kluwer Academic Publishers (  
http://www.wkap.nl/prod/b/1-4020-7739-4  ).

                John Barnes KS4GL, PE, NCE, ESDC Eng, SM IEEE
                dBi Corporation
                http://www.dbicorporation.com/
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