PURPOSE: To make the temperature of a material to be controlled such as a sample constant by connecting a current-heat conversion element to an output circuit for a complementary type transistor amplifier and applying the change of an electric signal based on the temperature change of a thermo-sensitive element to a control electrode for the amplifier.
CONSTITUTION: A thermistor 2 is connected between the base-collector of a transistor 5 as a voltage dividing resistor, and determines base potential together with a variable resistance element 3 connected between the base of the transistor 5 and a negative power supply V-. An emitter of the transistor 5 is connected to the negative power supply V- through a resistor RL1. Outputs from an amplification circuit are each applied to the positive and negative input terminals of a differential amplifier 6 through resistors RS1 and RS2. A feedback resistor RF determines the gains of an operational amplifier together with the input resistors RS1, RS2. An output from the operational amplifier is applied to each base electrode of an N-P-N type transistor 7 and a P-N-P type transistor 8 in common. A collector of the transistor 7 is connected to a positive power supply V+ and a collector of the transistor 8 to the negative power supply V-, each emitter is connected in common, and a Peltier element 9 is connected in between ground and transistors.
