Design Of The GaAs MESFET Distributed Amplifier

As the rapid development of Microelectronics and microwave communication technology, combined with increasing demanding for better performance of radio frequency integrated circuit at home and abroad, faster speed of device have been demanded. GaAs field-effect transistor (MESFET) is widely used in optical fiber communication, mobile communication, high-speed computers and measuring instruments, as well as space flight area due to its increasing electron mobility, high carrier drift velocity, large band gap, strong radiation resistance and wide operating temperature range. Currently, most of the integrated circuit design is based on ADS (Advanced Design System) software. The crucial factor for accuracy of circuit design is the equivalent circuit model of semiconductor devices exploitation, which is on the basis of accurate model parameters. In recent years, GaAs FET modeling and accurate extraction of model parameters have attracted the attention of scholars around the world.The small-signal model of NE72084 GaAs FET which was produced by Japanese NEC Corporation was investigated. First of all, the small signal S parameter of the device was measured with the bias of Vds=3V,Ids=10mA. Then small signal model of the device was created for parameter extraction of intrinsic and extrinsic components. Finally, the parameters' extraction results was imported to ADS software for simulation and optimization., Simulation results agree well with the measured data with the error precision below 10% in 2-18 GHz range.A 0-4GHz low-noise distributed amplifier was designed using NE72084 devices. An analytical optimization procedure including the cascaded common-source gain cell was done to debase the low frequency gain of the amplifier as well as improve the power gain.With the aid of ADS software, I carried out circuit simulation and optimization.As shown in the simulation results, the distributed amplifier has stable gain, superior gain-bandwidth with good input and output matching. Finally, the device model embedded in the distributed amplifier. Through the discussion of the intrinsic value's impact on circuit gain, the validity of small-signal model's parameters extraction is demonstrated.