Glossary
An engineer's dictionary of resistor and power-electronics terminology — definitions, formulas, units and concrete worked examples. Search by term, browse alphabetically, follow related links into our product catalogue and blog.
All terms (A–Z)
37 terms
A
AEC-Q200
AEC-Q200 is the qualification standard from the Automotive Electronics Council for passive components, defining stress-test conditions resistors must pass to be used in safety-critical automotive electronics from -40 °C to +155 °C.
Read full definitionAluminum-Housed Resistor
A power resistor in which a wirewound element is potted with silicone gel inside an extruded aluminum housing, designed to be bolted to a heatsink for high-density continuous power dissipation from 5 W to 1500 W.
Read full definitionAyrton-Perry Winding
A non-inductive wirewound construction with two counter-wound layers of resistance wire, achieving lower self-inductance than bifilar winding by also balancing inter-layer parasitic capacitance.
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B
Balance Resistor
A resistor connected in parallel with each capacitor in a series-connected capacitor bank to equalise the voltage across each unit and compensate for capacitance and leakage tolerances.
Read full definitionBifilar Winding
A non-inductive winding technique in which two parallel wires (or one folded wire) are wound side-by-side so opposing current directions cancel the magnetic field, dramatically lowering the resistor's self-inductance.
Read full definitionBleeder Resistor
A permanently connected resistor that drains residual energy from capacitors after power-off, ensuring the DC bus reaches a safe touch voltage (typically < 60 V) within a defined time per IEC 60204 / IEC 61851-23.
Read full definitionBraking Resistor
A resistor used to dissipate kinetic energy returned from a motor during deceleration in variable-frequency drives, servo systems, elevators, cranes and electric vehicles when regeneration to the grid is not possible.
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C
Cement-Encased Resistor
A power resistor in which a wound resistive element sits inside a ceramic shell filled with flame-retardant, inorganic cement, providing thermal mass, mechanical protection and UL94 V-0 safety performance.
Read full definitionContinuous Power
The maximum power a resistor can dissipate indefinitely at the specified ambient temperature and mounting without exceeding its long-term hot-spot temperature limit.
Read full definitionCurrent-Sense Resistor
A precision low-value resistor (typically 0.1 mΩ to 1 Ω) placed in series with a current path so the voltage developed across it, V = I × R, provides an accurate analog measurement of the current.
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D
Derating Curve
A graph that shows the maximum permissible power a resistor can dissipate as a function of ambient (or terminal) temperature, sloping linearly from 100 % at the rated temperature to 0 % at the maximum allowed operating temperature.
Read full definitionDuty Cycle
Duty cycle is the fraction of one period during which a resistor is dissipating power, expressed as a decimal or percentage; it converts a high peak power into an average power that the package thermal mass must absorb.
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F
I
IATF 16949
IATF 16949 is the global automotive quality management system standard, built on ISO 9001 and adding sector-specific requirements (PPAP, APQP, FMEA, statistical process control) that suppliers to automotive OEMs must follow.
Read full definitionIEC 60115 (Fixed Resistors)
IEC 60115 is the international standard series for fixed resistors used in electronic equipment, defining testing, marking and acceptance criteria for film, wirewound, network and other resistor types.
Read full definitionIEC 60322 (Wirewound Power Resistors)
IEC 60322 is the international specification for fixed wirewound power resistors above ~5 W, covering dimensions, climatic and mechanical tests, marking, derating and pass criteria specific to high-power industrial and traction applications.
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J
L
N
Noise Figure
For resistors, noise figure or noise index quantifies excess current noise above the unavoidable thermal (Johnson-Nyquist) floor, expressed in dB referenced to 1 μV/V of applied DC voltage per IEC 60195.
Read full definitionNon-Inductive Winding
A family of wirewound techniques (bifilar, Ayrton-Perry, reverse-layer) that reduce a resistor's self-inductance to negligible levels, enabling wirewound construction in high-frequency, pulse and switching applications.
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O
P
Peak Power
The highest instantaneous power level reached during a pulse or transient; for resistors it must remain below the pulse-power curve at the corresponding pulse width to avoid hot-spot damage.
Read full definitionPower Rating
Power rating is the maximum continuous electrical power, in watts, that a resistor can safely dissipate as heat at a specified reference temperature, typically 25 °C or 70 °C ambient.
Read full definitionPPM (Parts Per Million)
Parts per million is a dimensionless ratio equal to 1×10⁻⁶, used to express small relative quantities such as resistor TCR, tolerance drift, voltage-coefficient and long-term stability where percentage would lose resolution.
Read full definitionPre-charge Resistor
A current-limiting resistor placed between a DC source and a large DC-link capacitor bank during startup, charging the capacitors slowly through the resistor before the main contactor closes and bypasses it.
Read full definitionPulse Power
The instantaneous power a resistor can absorb during a short pulse of defined duration and duty cycle, often much greater than its continuous rating because the heat is buffered by the element's thermal mass.
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R
S
Snubber Resistor
A resistor in an RC or RCD network connected across a switching device (MOSFET, IGBT, diode, thyristor) to damp voltage transients, slow dV/dt and protect the semiconductor from over-voltage and oscillation.
Read full definitionSurge Withstand
A resistor's ability to absorb high-energy voltage or current surges (lightning, switching transients) without permanent change in value or open-circuit failure, characterised by standard waveforms such as 8/20 μs and 10/350 μs.
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T
TCR (Temperature Coefficient of Resistance)
TCR is the relative change in resistance per degree Celsius of temperature change, expressed in parts per million per kelvin (ppm/K or ppm/°C); it determines how stable a resistor is over its operating temperature range.
Read full definitionThermal EMF
Thermal EMF is the small Seebeck voltage generated at the junction of dissimilar metals when a temperature gradient exists across a resistor's terminations, typically 0.05–3 μV/°C, that can corrupt precision DC measurements.
Read full definitionThermal Resistance
The opposition a thermal path presents to heat flow, expressed in kelvins per watt (K/W); it directly determines how hot a resistor's body becomes for a given dissipation.
Read full definitionThick-Film Resistor
A resistor manufactured by screen-printing a paste of ruthenium-oxide and glass frit onto a ceramic substrate and firing it at ~850 °C; dominant in surface-mount chip resistors and high-voltage cylindrical types.
Read full definitionTolerance
The maximum allowable deviation of a resistor's actual resistance from its nominal value at room temperature and zero applied power, expressed as a percentage (e.g. ±1%, ±5%).
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V
VCR (Voltage Coefficient of Resistance)
VCR is the formal datasheet abbreviation for voltage coefficient of resistance, the relative change in resistance per applied volt, given in ppm/V; it is the dominant linearity spec for high-voltage and HV-divider resistors.
Read full definitionVoltage Coefficient
Voltage coefficient is the change in resistance value per applied volt across the element, expressed in ppm/V; it captures the non-linear behaviour of resistive elements under high electric fields.
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W
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