OPTIMIZING A GAAS HBT AMPLIFIER FOR MAXIMUM GAIN EFFICIENCY

The authors report a GaAs HBT amplifier which achieves a gain efficien cy of 2.14dB/mW at 17GHz which is believed to be among the highest rep orted for a self-biased MMIC in this frequency range. The amplifier's optimum gain bias was determined by finding the maxima of a simple bip olar gain-bias function which involves the graphical solution of a tra nscendental equation. This design calculation was experimentally verif ied for a four-stage Ku-band HBT amplifier which achieves 11.94dB gain at 17GHz while consuming only 5.6mW of DC power through a 1.88V suppl y. This method for optimising the gain efficiency can be applied to th e design of ultra-low DC power HBT gain blocks for communication and r adio-astronomy applications.