Voltage control of a buck converter
Integrated Inductive Switch-mode Power Supply. Fundamentals Feedback Loops : Voltage and Current Mode Controllers

Figure 1 recalls the functional structure of the buck converter where the switches are actually replaced by MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) transistors, available in CMOS semiconductor manufacturing technology. In simple terms the sw ₁ switch will be replaced by a so-called P-channel MOSFET transistor, and the sw ₂ switch by an N-type MOSFET transistor