A two-stage monolithic IF amplifier utilizing a Ta2O5capacitor

A two-stage monolithic IF amplifier incorporating a sputtered Ta2O5capacitor has been fabricated. The monolithic capacitor is based on a composite layer structure consisting of Au, Ta, Ta2O5, Ta, and Au. This layered structure is sequentially deposited in a single sputtering run, which eliminates particulate contamination. As a result, a thin pinhole-free dielectric layer can be deposited over large areas, and 140-pF capacitors have been fabricated with excellent yields. The large unit area capacitance of 1500 pF/mm²available with the present process has the potential for reducing the size of matching and bias circuits in microwave monolithic circuits and hybrid thin-film circuits. The monolithic amplifiers exhibit a gain of 17.5 ± 1.0 dB from 1.2 to 2.6 GHz and a minimum noise figure of ∼ 2.7 dB, with an associated gain of 17.5 dB at 1.7 GHz.