Monolithic microwave active inductors and their applications

Previously reported active inductors and their characteristics are reviewed. The most significant innovation of the active inductor is a novel circuit structure which suppresses stray capacitances to yield a much higher frequency operating range from a spiral inductor. Furthermore, the chip size of the active inductor is small and independent of the inductance value. Applications of the variable inductor with a very wide range, the miniature active combiner, and the voltage controllable oscillator composed of only an active inductor and a capacitor are demonstrated. These FET-oriented MMIC designs allow not only a denser chip circuitry but also a functionally enhanced MMIC implementation