A 3-watt X-band monolithic variable gain amplifier

The design and performance of a monolithic dual-gate GaAs FET 3-W X-band amplifier are discussed. The two-stage amplifier demonstrates 13-dB gain and over 20% power-added efficiency with low insertion phase variations over a 30% bandwidth. Both large-signal and small-signal gain can be varied by 20 dB while exhibiting less than +or-6 degrees insertion phase variation. The successful performance has established confidence in the utility of shunt in-line MIM tuning capacitors and large binary tree structures for on-chip power combining. In addition, this design has established confidence in the producibility of a large and fairly complex MMIC with substantial gate periphery, relatively large total MIM capacitance and many vias.<>