K-band F.E.T. amplifiers

The letter reports on 0.5-micron-gate GaAs FETs fabricated by a self-aligned technique. An equivalent circuit is used to model the measured S-parameters from 2 to 12 GHz and to generate S-parameters for the frequency range from 12 to 26 GHz, a unilateral device model is employed to design two circuits which conjugately match the FET input and output at 19 and 24 GHz, and the K-band S-parameters calculated from the equivalent circuit are utilized to model the device and computer-optimize the circuits. Amplifier gain and associated noise are plotted against frequency for the 19-GHz circuit as well as for two 24-GHz amplifiers biased and tuned for maximum gain. The results show a gain of about 9 dB from 18.5 to 20.5 GHz with no circuit tuning required, a gain of about 7.1 dB from 22.0 to 25.5 GHz for one amplifier, and a gain of about 8.0 dB from 23 to 26 GHz for the other. An amplifier noise figure of 5.6 dB is measured at 24 GHz with 5.0 dB of associated gain.