TSOP382838 IR receiver keeps outputting signal even if no infrared light is present
If you tune a cheap AM transistor radio to an unused channel you get noise coming out of the speaker because, in the absence of a proper radio transmission, the cheap automatic gain control just keeps raising its amplification and boosts the noise until it is at the same sort of level as it would expect for a proper incoming signal.

Do you see the comparison with what you have?