By John C. Pavlic, C-COR Electronics, Inc.
Many systems are being designed with amplifiers containing Feedforward technology because of its improved dynamic range over conventional push-pull hybrids. All Feedforward amplifying stages achieve this improved distortion performance by cancelling the distortion created in the stage's main amplifier. During the process of designing a Feedforward amplifying stage for use in trunk amplifiers, four circuits were modeled that would fulfill the basic requirements of a Feedforward amplifier stage. These four circuit models are presented with the operational advantages and disadvantages of each. In addition, the performance characteristics of several trunk stations using the most advantageous Feedforward circuit models are compared to each other and to conventional push-pull type trunk stations. The performance characteristics of several line extenders using the most advantageous Feedforward circuit models are also presented.