Negative Temperature Coefficient resistors or NTC are devices having a characteristic as shown in the figure. The resistance decreases when the temperature rises.

**Formula 1 **

Resistance of a NTC:

R = A x e^{B/T}

**Where: **

R is the resistance in a given temperature in ^{o}K in ohm (Ω)

A is a constant given by the manufacturer of the NTC.

B is a constant given by the characteristic (range from 1,000 to 8,000 ^{o}K)

T is the ambient temperature in degrees Kelvin (^{o}K)

**Formula 2 **

Resistance of a NTC II:

**Where:**

R is the resistance in a given temperature in ohm (Ω)

Rto is the resistance at To in ohm (Ω)

e = 2.71828

T is the final temperature in degrees Kelvin (^{o}K)

To is the reference temperature in degrees Kelvin (^{o}K)

B is a constant given by the component characteristic