Evolution of Solid-State Amplification and Its Limitations

Solid-state amplifying devices have two common features, 1) an inherent negative resistance, identified as the current or voltage source, and 2) a high electric field region, which manifests itself as the output impedance. A generalized equivalent circuit is developed using the above concepts. Several semiconductor amplifying devices are analyzed and their performances compared; the devices discussed include three-terminal devices, as well as twoterminal negative-resistance devices. The possibilities of increasing the gain-bandwidth product of semiconductor amplifiers is discussed and the additive-amplification technique for semiconductors is introduced.