A unique GaAs MESFET for low noise application

In most high performance microwave GaAs MESFETs, gate metal resistance contributes significantly to the noise figure. One solution to this problem is to parallel many short gate sections and to do this without significantly increasing the capacitive parasitics, the number of bonding pads, or die size. This paper describes a two-cell 750 micron device containing 28 gates in parallel, each gate being 27 microns wide and sub-micron in length, but having only four gate and two drain pads. The device is constructed using air-bridge drain-over-source crossovers, so that excess gate-to-source capacitance is avoided. Designed specifically for use in the 3.7 - 4.2 GHz communications band, the device has a noise figure of 0.9 dB with 13 dB associated gain at 4 GHz.