The amplification of weak signals into stronger signals is of fundamental importance in almost any electronic system. Sometimes this is obvious, as in a radio receiver, where the objective is to select and amplify the weak signal from the antenna and to present the detected signal via a loudspeaker. Sometimes the need for amplification is more subtle, as in an
electronic computer where no "circuit" labeled "amplifier" usually exists. Even here amplification is present and important; it may occur in each logic element or in only a few, but gain is necessary to ensure that the signal information is not lost in noise.
Because of the importance of amplifiers in the electronic art, we have tried to produce a work which will be of use to both students and engineers who have a need for a second look at amplifier theory from a more advanced point of view. We do not cover all types of amplifiers in complete or even partial detail. Rather, we review the fundamental principles underlying amplifier design and show several methods of design and synthesis which have proved useful in the past. Hence, we do not teach "all about amplifiers" but, rather, show some applicable modern methods and help the student extend these for himself.