This chapter discusses the design of impedance-matching circuits. It often is necessary to connect components or networks that have different impedances. If these components were to be indiscriminately connected, energy would be reflected between them, causing energy loss and other unwanted effects. We can use impedance-matching circuits between components in a network so that power is not 'bounced around' between them. Impedance-matching circuits are used in two ways. The most common application is to eliminate reflections between components or networks. Most transistors are not matched to the transmission lines that connect them; hence, small circuits are designed to match the input and output impedance of the transistor to the input and output transmission lines.