Original LM35 Temperature Sensor is an integrated analogue temperature sensor whose electrical output is proportional to Degree Centigrade. LM35 Temperature Sensor does not require any external calibration or trimming to provide typical accuracies. The LM35’s low output impedance, a linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy.
The main advantage of LM35 is that it is linear i.e. 10mv/°C which means for every degree rise in temperature the output of LM35 will rise by 10mv. So if the output of LM35 is 220mv/0.22V the temperature will be 22°C. So if the room temperature is 32°C then the output of LM35 will be 320mv i.e. 0.32V.
As such no extra components required to interface LM35 to ADC as the output of LM35 is linear with 10mv/degree scale. It can be directly interfaced to any 10 or 12 bit ADC. But if you are using an 8-bit ADC like ADC0808 or ADC0804 an amplifier section will be needed if you require to measure 1°C change.
LM35 can also be directly connected to Arduino. The output of LM35 temperature can also be given to comparator circuit and can be used for over-temperature indication or by using a simple relay can be used as a temperature controller.