in a device for thermal regulation of an enclosure comprising a temperature - measuring circuit which consists of a resistor bridge , of at least one heat - sensitive element on one bridge arm and of an amplifier , a control signal which is representative of the difference between the measured temperature of the enclosure and a reference temperature is delivered at the output of the amplifier . the absolute value of the control signal is adjusted by a negative feedback loop . a circuit for heating the enclosure is regulated by the temperature - measuring circuit and is constituted by at least one control transistor which delivers an adjustable heating current . the feedback loop of the output amplifier is mounted between the emitter resistor of the control transistor and the inverting input of the amplifier .