A Highly Linearized MMIC Amplifier Using a Combination of a Newly Developed LD-FET and D-FET Simultaneously Fabricated with a Self-Alignment/Selective Ion-Implantation Process


IEICE TRANSACTIONS on Electronics   Vol.E85-C    No.12    pp.1981-1989
Publication Date: 2002/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Low-Distortion,High-Power,High-Efficiency Active Device and Circuit Technology)
linearized amplifier,  MMIC,  MESFET,  self-alignment/selective ion-implantation process,  low-distortion,  

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We propose linearization techniques for MMIC amplifiers. The key points of these techniques are increased linearity of a newly-developed low-distortion MESFET (LD-FET) and maximized IP3 by combining the LD-FET with a high-gain depletion-mode MESFET (D-FET) with no increase in power consumption. The LD-FET is characterized by its unique channel dopant-profile prepared by a buried p-type ion-implantation and double n-type ion-implantations with high- and low-acceleration energies. This FET achieves flatter behavior in terms of mutual conductance (gm) compared with conventional MESFETs irrespective of changes in the gate bias voltage (Vgs). A self-alignment/selective ion-implantation process enables the LD-FET and D-FET to be fabricated simultaneously. This process encourages IP3 maximization of the multi-stage amplifier by appropriately combining the advantages of the two differently characterized MESFETs. We fabricated and tested a highly linearized two-stage MMIC amplifier utilizing the proposed techniques, and found that its third-order intermodulation ratio (IMR) performance was 8.7 dB better than that of conventional MMIC amplifiers at an input signal level of -20 dBm with no increase in current dissipation. The configuration constructed by using the proposed techniques equivalently reduces the current dissipation of the second stage to 1/2.72 times that of the conventional configuration, which requires a 2.72 times larger D-FET at the second stage to obtain an 8.7-dB IMR improvement. Furthermore, we were able to improve the IMR by 3.5 dB by optimizing the gate bias conditions for the LD-FET. These results confirm the validity of the proposed techniques.