A 2-20 GHz High-Gain Monolithic HEMT Distributed Amplifier

A low-noise 2-21 GHz monolithic distributed amplifier utilizing 0.35-micrometer-gate-length HEMT devices has achieved 12+-0.5 dB of gain. This represents the highest gain reported for a distributed amplifier using single FET gain cells. A record low noise figure of 3 dB was achieved midband (4-12 GHz). The circuit design utilizes five HEMT transistors of varying width with gates fabricated by E-beam lithography. The same amplifier fabricated with 0.35-µm-gate-length MESFET's in place of the HEMT devices resulted in 9.5+-0.5 dB of gain across the 2-20 GHz band. This record performance Ievel, for a MESFET distributed amplifier is used to determine that the use of HEMT devices rather than the small gate lengths is primarily responsible for the HEMT amplifier performance.