Tuned integrated circuits—A state-of-the-art survey

No completely satisfactory means for making an integrated circuit which is sharply frequency selective has yet been fully developed. The three general categories into which the various proposed solutions tend to fall, passive feedback, active feedback, and feedforward, are discussed. It is argued that only the passive feedback category is likely to produce solutions which are economically feasible for high frequencies and moderately high Q´s. Approaches coming under this category include an inductor using a thin-film ferrite, a transistorized version of the well-known reactance tube circuit, and acoustically resonant piezoelectric devices. A very promising new method of solidly mounting piezoelectric resonators and an acoustically resonant transistor are described.