The basic physical principles of construction of infrared photodetectors are described. Thermal, photonic, photoemission receivers, application of CCD in IR radiation receivers, nonlinear heterodyne reception are considered. The effect of various factors on the main parameters of photodetectors was analyzed. Maximum achievable values ​ ​ of parameters are indicated, a comparison is made with the level achieved experimentally. For engineers involved in the development and use of photodetectors.