A novel monolithic LNA integrating a common-source HEMT with an HBT Darlington amplifier

Here we report on the results of a novel HEMT-HBT LNA MMIC fabricated using selective molecular beam epitaxy (MBE) techniques. This unique circuit monolithically integrates a low-noise common-source HEMT with an HBT Darlington feedback amplifier to achieve high gain, low noise figure, and wide bandwidth utilizing a compact direct-coupled topology. The miniature direct-coupled MMIC is 0.9×0.7 mm² in size and obtains 1-8 GHz bandwidth, greater than 17.5 dB gain, and a minimum noise figure of 2.5 dB. The maximum IP3 is 18 dBm with a saturated output power (P_sat)>12 dBm. The HEMT-HBT amplifier achieves comparable P_sat performance to the conventional HBT-only Darlington amplifier while achieving over 2-dB reduction in noise figure across the band. This work benchmarks the first HEMT-HBT MMIC that illustrates microwave performance advantages when compared to an HBT-only design