Some Design Considerations for High-Frequency Transistor Amplifiers

Abstract

The major problem in the design of high-frequency transistor amplifiers is the interaction between the output and the input of the amplifier caused by the internal feedback of the transistor. This problem is illustrated and the two common design approaches to a solution of the problem are discussed. Nyquist's criterion of stability and Bode's feedback theory are then used to obtain an engineering evaluation of the relative merits of these two design approaches from a stability standpoint. The positive nature of the internal transistor feedback is established in this stability evaluation. Finally, Bode's feedback theory is used to consider the relative merits of some of the broad banding techniques used in transistor video amplifier design. The over-all analysis shows that many of the most practical and stable linear transistor amplifiers are very simple and can be built with a minimum of design effort.