Introduction to TES physics

Superconducting Transition Edge sensors (TES) devices are now in use across a broad range of applications including dark matter searches, gamma ray and x-ray spectroscopy, UV-optical-IR spectroscopy, IR bolometry and CMB bolometers. We summarize the effects that must be taken into account in the design of TES devices. These include determining time constants, maintaining voltage bias, avoiding electrothermal oscillations, critical current limitations, saturation and preventing normal-superconducting phase separation. We summarize our understanding of excess noise seen in most TES devices.