High-frequency tuned amplifier using integrated circuits

The design of IF amplifiers is discussed in which the circuit elements responsible for amplification, selectivity and (variable) attenuation are completely separated. This approach is possible using wide-band, fixed-gain integrated amplifiers with which it is not necessary to tune individual stages in order to obtain sufficient gain. An integrated amplifier with fixed gain, and bandwidth from direct current to 100 megacycles is described which can be used in this application. Methods of gain control and tuning are discussed, and their use illustrated in the design of a fixed gain 70-megacycle miniature IF amplifier and a variable gain 100-megacycle IF amplifier. The feasibility of using a single "universal" gain stage at any frequency within the above band makes the use of integrated circuits in analog systems more economically attractive.