Some Novel Characterisation Techniques Used in the Design of X-Band GaAs FET Amplifiers

Some improved techniques are described for characterising FETs at X-band frequencies. Device s-parameters are measured on an Automatic Network Analyser using co-axial calibration standards, and much better agreement has been obtained between theoretical and experimental amplifier responses. The measurement of minimum device noise figure, and more especially the accurate determination of optimum source impedance as a function of frequency, present some awkward problems at these frequencies. Some techniques will be presented which overcome many of these problems. The application of these techniques to practical amplifier fabrication will be illustrated by reference to several units, including a temperature compensated 9-10 GHz amplifier with 4.5 dB maximum noise figure, and a wide-band balanced amplifier.