Resistor (1/4 W carbon film) Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

Axial (CFR-25)

Physical pin numbers2 pins

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Resistor (1/4 W carbon film) pin functions and connections
Pin	Signal	Type	Function & connection
	1	Terminal 1	One end of the resistive film. A resistor has no polarity: either end can face the supply. Connection guidance Connect in series with the part whose current it limits, or as the top of a divider. Power P = I² × R is shared by the whole body; the leads carry heat away.
	2	Terminal 2	The other end of the film, identical to terminal 1. Connection guidance Connect to the rest of the circuit or toward ground. Keep the body clear of the board when it runs warm.

Manufacturer scope and page conventions

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Reference	YAGEO CFR series, product specification 2 Sep 2022	CFR-25 column (1/4 W)
Construction	Carbon film on a ceramic core, helically trimmed	Lacquer coated, colour bands
Default part	CFR-25JB-52-1K	1 kΩ, ±5 % (J), bulk
Polarity	None	Pins 1 and 2 are interchangeable
Footprint	RES40 · 10.16 mm (0.4 in) between pads	Leads formed for a board; YAGEO M-forming is 10.0 ± 1 mm
Values	E24 series, 1 Ω to 10 MΩ	±2 % (G) or ±5 % (J)

The colour code is the same for every through-hole resistor; the power rating is not, so check the body size.

CFR-25 · 1/4 W

Manufacturer-referenced values7 parameters

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Parameter	Value	Conditions / notes
Power rating	0.25 W	At 70 °C ambient
Derating	100 % up to 70 °C, linearly to 0 % at 155 °C	Ambient temperature
Maximum working voltage	250 V	And never above the rated continuous working voltage √(P × R)
Maximum overload voltage	500 V	Short-time overload test limit
Dielectric withstanding voltage	500 V for 60 s	V-block, no breakdown
Operating temperature	−55 to +155 °C	Recommended range
Peak pulse power	66 W up to 10 µs, about 0.58 W at 1 s	Single pulse, from the pulse diagram

RCWV = √(P × R): a 1 kΩ part reaches its power at 15.8 V; above 250 kΩ the 250 V limit applies first.

Maximum change per °C

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
Below 100 kΩ	−500 to +350 ppm/°C	Carbon film usually falls slightly as it warms
100 kΩ to 1 MΩ	−700 to 0 ppm/°C	Maximum
1 MΩ to 10 MΩ	−1500 to 0 ppm/°C	Maximum
Example	1 kΩ at −300 ppm/°C heated by 50 °C	R = 1000 × (1 − 0.0003 × 50) = 985 Ω
Thermal resistance	About 340 °C/W in free air	(155 − 70) °C / 0.25 W

Use metal film (±50 ppm/°C or better) where a divider must stay accurate over temperature.

IEC 60115-1 · allowed resistance change

Manufacturer-referenced values8 parameters

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Test	Condition	Allowed change
Short-time overload (4.13)	2.5 × RCWV for 5 s, never above 500 V	±(0.75 % + 0.05 Ω)
Periodic-pulse overload (4.39)	4 × RCWV (or Umax), 10 000 cycles of 1 s on, 25 s off	±(1 % + 0.05 Ω)
Endurance at 70 °C (4.25)	RCWV for 1000 h (1.5 h on, 0.5 h off)	±(3 % + 0.05 Ω)
Damp heat (4.24)	40 °C, 90–95 % RH, 56 days at 0.1 × RCWV	±(3 % + 0.05 Ω)
Temperature cycling (4.19)	−55 °C ↔ +155 °C, 5 cycles	±(1 % + 0.05 Ω)
Soldering heat (4.18)	260 °C for 10 s, 3 mm from the body	±(1 % + 0.05 Ω)
Insulation resistance (4.6)	V-block, 60 s	> 1000 MΩ
Robustness of terminations (4.16)	Pull along the leads for 10 s	≥ 24.5 N (2.5 kg)

These are qualification tests of the part, not normal operating conditions.

Four-band through-hole resistors

Manufacturer-referenced values12 parameters

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Colour	Digit	Multiplier	Tolerance
Black	0	× 1	—
Brown	1	× 10	±1 %
Red	2	× 100	±2 %
Orange	3	× 1 k	—
Yellow	4	× 10 k	—
Green	5	× 100 k	±0.5 %
Blue	6	× 1 M	±0.25 %
Violet	7	× 10 M	±0.1 %
Grey	8	—	—
White	9	—	—
Gold	—	× 0.1	±5 %
Silver	—	× 0.01	±10 %

Read from the end nearest a band: 220 Ω is red–red–brown–gold, 1 kΩ brown–black–red–gold, 10 kΩ brown–black–orange–gold.

LED current limit and a voltage divider

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
LED from 5 V, red (Vf 1.85 V)	220 Ω → 14.3 mA	(5 − 1.85) / 220
Power in that resistor	45 mW	0.0143² × 220; 18 % of 1/4 W
Divider from 9 V	10 kΩ over 4.7 kΩ → 2.88 V	9 × 4.7 / (10 + 4.7)
Divider current and power	0.61 mA · 3.8 mW in the 10 kΩ	Loading the output lowers it
What burns	100 Ω across 9 V: 810 mW	3.2 × the rating; the film opens within seconds

ProTech’s resistor example runs all of these, including the burnout.

CFR-25JB-52-1K · Axial (CFR-25)

Manufacturer-referenced values5 parameters

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Parameter	Value	Conditions / notes
Body length	6.3 ± 0.5 mm	CFR-25
Body diameter	2.4 ± 0.2 mm	Lacquered, colour bands
Leads	Ø 0.55 ± 0.05 mm, 28 ± 2 mm long	Tinned copper
Formed for a board	10.0 ± 1 mm between bent leads	YAGEO M type
Footprint	RES40: pads 1 and 2, 10.16 mm apart	1.778 mm round pads, 0.762 mm drill · Through-hole

Leave 1–2 mm between the body and the board for parts that run warm.