In this book the author's aim has been to present in a compact and logical way the basic principles involved in the design and analysis of linear a.c. circuits with particular attention to the properties of the linear amplifier and its use in feedback systems. For the sake of brevity the author has not specifically discussed the characteristics of any active device other than the silicon transistor, and has offered no explanation of mathematical techniques such as complex algebra, Fourier analysis etc. which are already more than adequately covered in textbooks of mathematics.