Скачать или смотреть Thermometer Sensor Circuit Explained with Op Amp and NPN Transistor

Thermometer Sensor Design and Operation are explained in this video. A single Op Amp, an NPN BJT transistor, two Zener Diodes and two potentiometers are used to design this thermometer sensor circuit. The PN junction of the NPN transistor is serving as temperature probe in this circuit. The value of variable resistors R1 and R2 are computed in this video so that the output voltage of the circuit is approximately zero when the PN junction temperature is at zero degree Celsius. And increases 100 mV per degree Celsius increase in junction temperature. Effectively the output voltage of this thermometer circuit is proportional to the measured temperature. The series of two carefully selected Zener diodes provide us with a robust 8.2v reference voltage with a very small temperature sensitivity of 25 micro Volt per degree C to support excellent temporal thermometer accuracy. A combination of virtual short for the operational amplifier operating in linear region, KCL and KVL are used to find the needed two equations to solve for the two unknowns which are the desired values of the two potentiometers in this circuit.