Broadband Lumped Element X-Band GaAS FET Amplifiers

The GaAs FET is increasing in use as a high frequency, low noise amplifier. This paper presents work directed to extending the band-width and repeatability of X-band FET amplifiers by the use of lumped element techniques. Such lumped element microwave circuits offer a considerable size saving when compared to microstrip circuits. Two approaches are described - one a conventional hybrid broadband lumped amplifier and the other a monolithic amplifier. The monolithic amplifier has lumped matching components combined with the FET on the GaAs chip. These approaches have yielded three stage amplifiers having 16 dB (±1 dB) gain over the frequency range 6.5 - 12 GHz. A balanced amplifier module suitable for X-band systems is also described.