Through-Hole Resistor
A through-hole resistor is the classic axial-leaded resistor with two wire leads bent into PCB holes. It's larger, more thermally robust, and easier to hand-solder than its surface-mount counterpart.
A leaded resistor contains a resistive element and electrical terminations in a protective body. Construction varies between carbon-film, metal-film, wirewound and other designs. Color bands or printed markings identify value and tolerance; some marking schemes also identify temperature coefficient. Do not assume every resistor has a temperature-coefficient band.
In plain terms
Imagine a wide pipe with one narrow section. Water still flows, but the narrow part forces a pressure drop. A resistor is that narrow section for electric charge.
Why designers use it
- Through-hole prototypes and breadboards where SMD parts are inconvenient.
- Educational kits and repair work where leaded components are easier to handle.
- High-power applications where the larger thermal mass tolerates several watts.
- Vintage and audiophile gear where a leaded part's parasitics are part of the design.
Best for
- Breadboarding
- High-power dissipation
- Hand assembly
- Repairs
Key specifications
- Range: 0.1 Ω – 100 MΩ
- Tolerance: ±0.1 % – ±10 %
- Power: 1/8 W – 5 W
- Tempco: ±50 – ±200 ppm/°C
- Body length: 3 – 25 mm
When not to use it
- On dense modern PCBs — they take 4–8× the area of an equivalent chip resistor and slow pick-and-place.
- In high-frequency circuits — the lead inductance becomes significant above 100 MHz.
- Where the BOM cost matters at scale — through-hole parts cost more to assemble than SMD even when the part itself is cheaper.
Common mistakes
- Reading the color bands wrong — gold and silver multipliers vs. gold and silver tolerance bands trip up beginners.
- Underestimating the body-temperature rise on a 1 W carbon film — they discolor and drift well before the rated power.
- Cutting leads flush with the board so the joint has no strain relief and cracks from mechanical stress.
Where you will find it
- A laboratory bench power supply uses wirewound through-hole resistors as bleeder resistors across its output capacitors: their 5 W rating lets them safely dissipate the stored energy when the supply is switched off, so the output discharges to zero instead of holding a hazardous voltage.
- An audio effects pedal uses 470 kΩ carbon-film through-hole resistors as the input-bias resistors to its op-amp: the hand-assembled design benefits from the resistor's easy replaceability and visual colour-code identification during repair.
- A broadcast transmitter's dummy load consists of ceramic wirewound through-hole power resistors: they absorb the full 50 W RF output during testing and fault diagnosis, converting the transmitter's power cleanly to heat without radiating anything that would interfere with aircraft communications.
A short history
A through-hole resistor has leads that pass through holes in a circuit board and are soldered in place. Its resistance creates a voltage drop when current flows, allowing it to limit current or form part of a voltage divider. Choose its resistance and ratings for the circuit, not just its mounting style.
Good to know
- Carbon-composition through-hole resistors (1928) were the first commercial resistor type; their behaviour under high-energy pulses is unique — they degrade gracefully where modern parts vapourise.
- Metal-film through-hole resistors (1950s) brought 1 % tolerance to the masses; the colour-band code adds an extra band for the multiplier when 1 % becomes the norm.
- Wirewound resistors are the only type that's truly inductive — a 5 W axial wirewound has tens of µH and rings if you put a square wave across it.