Two-Stage High-Gain High-Power Distributed Amplifier Using Dual-Gate GaN HEMTs

A two-stage distributed amplifier monolithic microwave integrated circuit (MMIC) has been designed and fabricated using dual-gate GaN HEMTs. The measured small-signal gain of the MMIC is about 20 dB over the frequency range of 2-18 GHz. Measured peak saturated output power is about 2 W. A low interstage impedance of 25 Ω is chosen for two reasons. It leads to larger size of the HEMTs in the output stage, and hence, increases output power without reducing the bandwidth. It also keeps the inter-stage transmission lines short, and hence, results in a very compact two-stage design with high gain. To enhance the output power further, capacitive division technique is used in the second stage. Dual-gate HEMTs are used, as they are compact and provide superior performance when compared to standard HEMTs.