Such an increase is duo to resistive ballast used and can be understood in terms of a
negative temperature coefficient of the LEDs forward voltage, which has typical values of about -2 mV/[degrees]C.
Most thermistors have a
negative temperature coefficient, where resistance decreases as temperature rises.
The cubic [SrTiO.sub.3] phase has a high dielectric constant but a
negative temperature coefficient. This is a potentially useful microwave ceramic that requires second-phase compensation.
The first is a power-sensing termination, which is based on a linear
negative temperature coefficient (NTC) thick-film thermistor used in combination with a linear positive temperature coefficient (FTC) material to convert RF power to DC voltage.
The objective of this paper is to show that conductive polymer composites produced by hot compaction of a mixture of carbon black and ultra-high molecular weight polyethylene powder exhibit a large positive temperature coefficient (PTC) and no
negative temperature coefficient (NTC) effects even at temperatures significantly above the melting point of the polymer.
Materials with a
negative temperature coefficient of dielectric constant are used for compensation of oscillators and VCOs exhibiting a negative frequency and temperature coefficient.