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LM135 temperature sensor and its application circuit

Published on Mar 11 2011 // Device application circuits

 LM135 temperature sensor and its application circuit 1

LM135/235/335 National Semiconductor has introduced a precision temperature sensor, it works similar to zener diodes, the reverse breakdown voltage with temperature at +10 mV / k changes in the law can be used in precision temperature measurement equipment. There are three types of packages required for the instrumentation requirements, and its main features are as follows:
Absolute temperature scale calibrated directly in
Accuracy of 1
Current 400uA-5mA
1O dynamic impedance
Easy calibration
Wide operating temperature range of 2001
Low-cost

LM135 temperature sensor and its application circuit 2

Figure 2 is an internal schematic diagram LM135, V15 and V16 is a temperature sensing element, the physical structure of the two transistors have a specific requirement, V15 V16 emission emitter junction area is 10 times the area. They are exactly the same collector load resistance, resistance if the flow of current through these two different, V15 and V16 of the collector voltage is different, composed by V1-V8 differential amplifier, V1 also changed the internal resistance, then Liu had will change the current Rs, V + and V-between the voltage also changes the voltage variation with temperature is changing.

 LM135 temperature sensor and its application circuit 3

LM135 temperature sensor and its application circuit 4

LM135V + and the voltage difference between  V is proportional with the ambient temperature changes only, and access to 10mV / K sensitivity of output.

 LM135 temperature sensor and its application circuit 5

The main electrical indicators are LM135V

 LM135 temperature sensor and its application circuit 6