LM335-based Temperature Sensor Circuit

Figure 1.  Circuit Diagram for Temperature Sensor Circuit

This is a temperature sensor circuit that uses an LM335, an IC that converts the ambient temperature into an equivalent output voltage. The voltage output of an LM335 increases by approximately 10 mV for every 1 degree Kelvin of rise in temperature. Note that 1 degree Kelvin is equal to 1 degree Celsius.

In the circuit, the output of the LM335 is fed into a 741 op-amp (any standard op-amp may be used) which is configured as a voltage follower.  As such, the output of the 741 is the same as the voltage output of the LM335. The main function of the op-amp, therefore, is just to buffer the LM335 output so that it is not affected by whatever load is connected to this temperature sensor circuit.

Correlation of the ambient temperature to the output voltage of the circuit using a thermometer and a voltmeter is needed if the circuit is to be used for measurement purposes.