Chapter I introduces the basic principles of transistors. In the following chapters the applications of these devices in a wide variety of circuits are discussed. Chapters 2 to 5 inclusive discuss the ways in which transistors and integrated circuits can be used for the amplification of signals. In chapters 3 and 4 the gain of an amplifier has sometimes been expressed as 20 log10 (the voltage gain) dB even when the input and output impedances are (probably) not equal. This is the usual practice when considering Bode diagrams and the stability of feedback amplifiers and does lead to some simplification of problems.