Body effect
The body effect (also known as substrate bias effect) is an undesired second-order effect present in field-effect transistors (MOSFET) that describes the change in transistor's threshold voltage ( V t h {\displaystyle V_{th}} ) resulting from a potential difference between the source and the bulk (substrate) terminals. While ideal first-order MOSFET models assume that the source and bulk are tied to the same potential, in many integrated circuit topologies the source voltage varies dynamically while the substrate is kept at a global reference potential.