Stable source of infrared radiation for photometer calibration

The emitted power is stabilized by keeping the LED temperature constant and by feeding it from a constant-current generator composed of field-effect transistor (FET) T1 (KP902A), operational amplifier M1 (140UD7), resistors R1 and R2, and zener-diode voltage stabilizer D2 (D818E). The generator output current is 80 mA, the stabilization error not exceeding 0.05% for • changes of ambient temperature.