Abstract: A temperature controlled circuit including a thermistor located in one branch of a bridge circuit containing several resistors, an operational amplifier, all combined in such a manner that a resistor is inserted in parallel with the thermistor to lower its impedance. The branches of the bridge circuit are also arranged in such a way that three branches have a nominal resistance approximately equal to the resistance of the thermistor in parallel with its fixed resistance at room temperature, while the fourth leg on the branch in series with the parallel thermistor and resistance across the voltage source will have a resistance nominally in the range of one-third of the paralleled resistor and thermistor. The arrangement is such that most any thermistor can be utilized merely by changing its parallel resistance, and the operational amplifier will operate with the thermistor over a wide temperature range.