Abstract :
Wherever parasitic impedances are found shunting the terminals of a network, certain limitations on the electrical behavior of this network can be found. Typically, these parasitic impedances might represent a transistor, vacuum tube, or some other loading effect. In this paper, theoretical limitations are derived for the gain-bandwidth product of passive linear three-terminal networks (not necessarily lossless) used as low-pass filters. An important use of these limitations is in determining the upper bounds on the performance of video amplifiers. Bode has considered limitations of this type for an important but restricted class of networks where the parasitic elements are purely capacitive, whereas in this paper, limitations are shown for arbitrary parasitic impedances. One important application of this new generality is that limitations can now be established for transistor amplifiers. This development has required the use of a general resistance integral theorem, the derivation of which is given in this paper. Different limitations are indicated for RLC networks and those allowing mutual inductance. Examples are given.
