There is currently no animal model available that allows chronic control of body temperature, e.g. to study the effects of body temperature on disease. Prior studies have shown that by heating the preoptic area (POA) of the hypothalamus of rodents with a heated water-perfused probe the body temperature can be lowered, but this method is not feasible for chronic use. Here we present two control circuit designs that employ high performance operational amplifiers and a feedback network that has the ability to chronically modulate the temperature of the POA of the hypothalamus, thus adjusting the body temperature set point. This will be done by permanently implanting a heated micro-probe (thermistor) and using a feedback system to accurately control the temperature of the thermistor to help the brain center control the temperature. The control circuit and feedback network were designed to provide accurate and sustainable control over the subjects body temperature while focusing on the miniaturization of components without sacrificing performance. For this design the power consumed by the circuit was achieved to be 3.8 mW and the size of the board is currently 9 cm2. Tadiran batteries were used to employ high-performance button cells. The thermistor used is around 360 μm and it is capable of controlling the temperature between 98.6 °F/37 °C and 122 °F/50 °C. Thus, the circuit is sufficiently small to be carried by a rodent while chronically controlling the POA temperature.