Cascadable Monolithic Balanced Amplifiers at Microwave Frequencies

摘要

A cascadable monolithic amplifier, where input-output decoupling is obtained through broad band, low loss coplanar directional couplers, is described. Design data and experimental results are given for the couplers which are suitable for both hybrid and monolithic circuit applications. For the amplifier, a single point matching technique was sufficient to obtain a flat gain over the selected bandwidth. Matching at the upper frequency limit is achieved through series and parallel inductances. The latter ones, dc insulated from ground by 0.4 micron thick SiO2 MIM capacitors, were used as biasing networks. A 0.8 micron gate self aligned field effect transistor was employed as an active device, whick allowed 10 dB gain to be obtained from 9 to 11 GHz. The simplicity of matching circuits allowed single stage minor akjustments from wafer to wafer, which were found unnecessary when correlated to a proper dc device characterization. Passive circuit metallization was 3 micron thick electrolytic gold directly grown on the first Au Ge layer, obtained by the liftoff process.