This lecture covers the use of silicon resistors as thermal sensors, focusing on the relationship between temperature and resistance in silicon-based devices. It explains the impact of temperature on carrier density and resistance, as well as the functioning of diode-based thermometers. The instructor discusses the concept of reverse saturation current and the direct current flow through diodes. Additionally, the lecture explores differential measurements to eliminate temperature-dependent effects and the integration of PTAT sensors into circuits. It concludes with a detailed explanation of thermocouples as thermal sensors.