One source: There is always noise from the electrons in the wires, moving about because they have thermal energy. If your signal is weak and you turn up the gain (aka ISO in a digital camera) then it can amplify this noise up along with the signal. The thermal noise can be reduced by cooling the electronics. At absolute zero there would be no thermal noise..
MyTVC_16
joined 10 months ago
The chemicals in the plastic packaging on the electronics chips (including transistors) slowly leaches into the silicon and will eventually mess up the semiconductor characteristics, causing them to fail..