Microwave Monolithic Broadband Amplifier Design Studies

This paper mainly introduces the design of Monolithic Microwave Integrated Circuit (MMIC) wideband amplifier. The principles and the design of the circuits are given. The evolved history and the advantages of MMIC are introduced firstly. Then the structure characteristic of PHEMT, small-signal and large-signal model parameter extraction method for PHEMT model are presented in the paper. The paper emphasis on the design of broadband amplifer, based on the design index, the matching circuits, bias and stability circuits as well as topology structure are all designd. Simulation and optimization of the circuits are under the Agilent ADS software.A 6～20GHz broadband MMIC medium-power amplifier based on 0.25μm power PHEMT process is designd. The amplifier has two stages, the first stage PHEMT with gate width of 4×35μm was used to drive the second PHEMT with gate width of 4×70μm. With a single 5-volt DC power supply, each stage works at class-A operation for optimal power output with minimal distortion. The two-stage feedback amplifier has 18.0±0.2dB small signal gain with 3.7dB typical noise figure and input and output VSWRs are less than 1.7 over 6～20GHz. The output power at 1dB gain compression are more than 18.5dBm, the designing simulation results indicate that this method is simple and feasible.A 3.5～7GHz broadband MMIC low noise amplifier based on 0.25μm low-noise PHEMT process is designd. We also adopt two-stage working method, having 3-volt DC power supply. It achieves a noise factor of less than 1.8dB, a gain of more than 15.5 dB with flatness of less than±0.5dB, input and output VSWRs are less than 1.7 across the band. The results show that it achieves the requirement of design objective.