A broadband low noise dual gate FET distributed amplifier

Abstract

A 2 to 18 GHz monolithic GaAs low-noise distributed amplifier with 10 dB nominal gain was designed and built using the standard Texas Instrument GaAs foundry process. This process incorporates ground vias, metal-insulator-metal (MIM) capacitors and air bridges. The amplifier uses 0.5- mu m-gate ion-implanted dual-gate FETs (DGFETs). The noise figure is less than 5.7 dB over the 2 to 18 GHz band and less than 4.0 dB from 3 to 13 GHz. The DGFET amplifier provides gain control capability; with 5 V and 60 mA operating bias it provides 10-dB nominal gain, input return loss better than 10 dB, and output return loss better than 8 dB. Lower power consumption was demonstrated at 5 V and 30 mA. With this reduced bias the nominal gain drops to 8 dB and the noise figure degrades by 0.3 dB. Increasing the bias to 7 V and 90 mA increases the nominal gain to 11 dB while degrading the noise figure by 0.3 dB. This increased bias gives the amplifier medium power capability, with a 1-dB gain compression power output of 18 dBm at 18 GHz. This increases to 19 dBm for frequencies below 15 GHz.<>