scope:
This specification covers the general requirements for molded, dipped, and potted mica dielectric, fixed capacitors intended primarily for use in high stability, low-loss radio-frequency applications such as tuned circuits (see 6.1). This is a graded specification covering ranges in temperature coefficient, capacitance, tolerance, temperature, and vibration.
The type designation shall be in the following form, and as specified (see 3.1 and 6.2):
The style is identified by the two-letter symbol "CM" followed by a two-digit number; the letters identify/mica dielectric, fixed capacitors, and the number identifies the shape and dimensions of the capacitor.
The characteristic is identified by a single letter which indicates the relative stability of the capacitor with temperature change, in accordance with table I.
TABLE I. Characteristic.
Symbol Temperature coefficient Capacitance drift
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Parts/million/°C
B - - - - - - - - - - - Not specified Not specified
C - - - - - - - - - - - −200 to +200 ±(0.5 percent +0.1 pF)
D - - - - - - - - - - - −100 to +100 ±(0.3 percent +0.1 pF)
E - - - - - - - - - - - −20 to +100 ±(0.1 percent +0.1 pF)
F - - - - - - - - - - - 0 to +70 ±(0.05 percent +0.1 pF)
The voltage rating is identified by a single letter in accordance with table II.
TABLE II. Voltage rating.
Symbol Voltage Symbol Voltage Symbol Voltage
rating rating rating
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volts, dc volts, dc volts, dc
A- - - - - 100 J- - - - - 2,000 R- - - - - 10,000
B- - - - - 250 K- - - - - 2,500 S- - - - - 12,000
C- - - - - 300 L- - - - - 3,000 T- - - - - . 15,000
D- - - - - 500 M- - - - - 4,000 U- - - - - 20,000
E- - - - - 600 N- - - - - 5,000 V- - - - - 25,000
F- - - - - 1,000 P- - - - - 6,000 W- - - - - 30,000
G- - - - - 1,200 Q- - - - - 8,000 X- - - - - 35,000
H- - - - - 1,500
The nominal capacitance value expressed in picofarads (pF) is identified by a three-digit number; the first two digits represent significant figures and the last digit specifies the number of zeros to follow.
The capacitance tolerance is identified by a single letter in accordance with table III.
TABLE III. Capacitance tolerance.
Symbol Capacitance tolerance
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D - - - - - - - - ±.5 pF
F - - - - - - - - ±1%
G - - - - - - - - ±2%
J - - - - - - - - ±5%
K - - - - - - - - ±10%
The temperature range is identified by a single letter in accordance with table IV.
TABLE IV. Operating temperature range.
Symbol Operating
temperature range
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M- - - - - - - - −55° to +70°C
N- - - - - - - - −55° to +85°C
O- - - - - - - - −55° to +125°C
P- - - - - - - - −55° to +150°C
The vibration grade is identified by a single digit in accordance with table V.
TABLE V. Vibration grade.
Symbol Vibration condition
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1 - - - - - - - - 10 to 55 Hz
3 - - - - - - - - 10 to 2,000 Hz
intended Use:
These mica capacitors, because of their low-power factor, high breakdown voltage, low-dielectric absorption, and high-insulation resistance, are intended for use in high-frequency circuits where... View More
These mica capacitors, because of their low-power factor, high breakdown voltage, low-dielectric absorption, and high-insulation resistance, are intended for use in high-frequency circuits where good stability is required for temperature, frequency, and aging, such as in timing and frequency-determining circuits.
The voltage ratings specified (see 3.1) apply over the operating temperature range of the capacitor, and under the following conditions:
(a) Barometric pressure - As specified in the associated specification sheet for altitudes up to 50,000 feet for the larger transmitting styles and 100,000 feet for the remaining styles.
(b) Relative humidity - Up to 80 percent.
Current ratings for potted capacitors at various frequencies are as specified (see 3.1), and apply under conditions of ancient temperatures up to 30°C and barometric pressures between 28 and 32 inches of mercury, with the capacitors supported so as to allow free air on all sides. Rating factors for maximum safe operating currents at higher temperatures are given in table XIII.
TABLE XIII. Maximum safe operating currents at high temperature.
Ambient temperature Rating factor in percent
of rated current
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°C
50- - - - - - - - - - - - - - - - - - - 95
60- - - - - - - - - - - - - - - - - - - 85
70- - - - - - - - - - - - - - - - - - - 70
It should be noted that this specification contains no requirements concerning the flammability of the materials used in the capacitors. Users should take this into consideration when a particular application involves this requirement.
For dissipation factor measurement purposes Q= 1/DF (see 3.8.1).
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