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 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.