The amplifying path of a modern miniature medical radiothermograph should provide a gain of about 80 dB with minimal intrinsic noise levels. The construction of such a path, even on the most modern element base, requires the use of several microcircuits with a significant resulting current consumption. The existing problem can be solved by creating new active elements of specialized monolithic microcircuits - low-noise transistors, for which the requirements of high energy efficiency will be taken into account when designing heterostructures. The paper presents the results of optimizing the design of a heterostructure low-noise transistor for use in microcircuits of the amplifying path of a miniature medical radiothermograph.