ERT-J1VA220J Datasheet, PDF (1/14 Pages) Panasonic Semiconductor – The NTC Thermistors

NTC Thermistors
The NTC Thermistors
This is a Negative Temperature Coefficient Resistor whose resistance changes as ambient temperature changes. Therm-
istor comprises 2 or 4 kinds of metal oxides of iron, nickel, cobalt, manganese and copper, being shaped and sintered
at high temperature (1200 to 1500 °C)
■ Features
● Temperature Coefficient of Resistance is negative and
extremely large
● Various kinds of types especially smaller ones are
available.
● Resistance values are available from 22 Ω to 470 kΩ
■ Recommended Applications
● For temperature measurement or temperature detection :
thermometer, temperature controller
● For temperature compensation : transistor circuit,
measuring instruments
■ Physical Characteristics of NTC Thermistors
Thermistor is a resistor sensitive to temperature utilizing
the large temperature-coefficient of metal oxide semi-
conductor. And its temperature dependency of resistance
value is indicated by the following equation:
[ ( )] ^{R=R0 exp B}
11
T T0
.................................... ₍₁₎
T0: Standard Temperature 298.15 K(25 °C)
R0: Resistance at T0 K
B: Thermistor Constant (K)
So called Temperature Coefficient (a) is generally
indicated as follows:
a=
B
T²
.................................................................... ₍₂₎
But a is not adequate for use as a constant, because a
change by temperature is considerably large, so B Value
is used as a coefficient of thermistor.
Fig. 1
1000
100
10
1
B=1000
2000
0.1
3000
4000
5000
0.01
6000
0.001–40 _{–20 0}
20 40 60 80 100 120 140
T (˚C)
■ Major Characteristics of NTC Thermistors
The relation between resistance and temperature of a
thermistor is linear as shown in Fig. 2, in which resistance
is shown in vertical direction in a logarithmic scale and
reciprocal of absolute temperature in horizontal direction.
Bias degrees in these straight lines are determined according
to the B Value expressed by the following equation.
B = ^{knR1 – knR2}
11
T1 T2
.................................................. ₍₃₎
R1: Resistance at T1 K
R2: Resistance at T2 K
When calculated from this equation, B Value is a variable
in a strict sense, and the resistance is expressed by the
following equation:
R = AT^–C exp D/T........................................................ (4)
In (4), C is a small positive or negative constant and quite
negligible except use in precision temperature-measuring
device, thereby the B Value is, in practical usage, to be
considered as a constant. In Fig. 1,
the relation between the resistance ratio RT/R25
(R25: Resistance at 25 °C, RT: Resistance at T °C) and B Value is
shown with T °C, in the horizontal direction.
Fig. 2
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100000
10000
1000
100
10
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₅₂₂₅^B0=_/55/58^2//4₀₅₅⁵⁵₌^0/0=75==0₂₀₃^=440844520₀₃₀₅⁵₀₅₀₀⁰
1
2.4
125
2.9 ₁
T
3.4
(L10 ^–3K^–1)
85 50 25
0
T (˚C)
3.9
–20
4.4
–40
00 Sep. 2010