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/ ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu