A 170-mW class GaAs Power MESFET and a 10-mW class MMIC pre-amplifier operating at very low drain bias have been developed for use in personal handy phones (PHP). The MESFET provided P0(1dB)22.5 dBm, ηadd38.8% at VDS3 V with IDS0.14 A (0.4 IDSS) at 1.9 GHz, and also provided P0(1dB)22.4 dBm, ηadd32.6% at VDS2 V with IDS0.24 A (0.6 IDSS). The MMIC using the same MESFET structure had a linear power gain of 13 dB, a linear output power of more than 10 dBm, and P0(1dB)13.7 dBm, ηadd24.3% at VDD3 V with ID30 mA at 1.9 GHz. The MESFET had a buried p-layer and our improved LDD n self-aligned structure both of which were optimized so as to satisfy a high V(BR)GDO of more than 10 V, a minimized bias dependence of S-parameters and low VK of less than 0.5 V.

An integrated CAD/CAM system for MMIC development has been firstly realized, which consists of electron beam direct drawing, microwave circuit simulator, pattern generator and RF &DC on-wafer automatic measurement subsystems, connected through an Ethernet LAN. The system can develop not only new MMICs and their element devices, but also their accurate simulation models quickly and efficiently. Preliminary successful applications of this system have been demonstrated by DC-HFET with a 0.25 µm T-shaped gate electrode and MMIC low-noise amplifiers operating at X- and L-bands.