Monolithic millimetre-wave amplifiers

Ultra-wideband monolithic HEMT amplifiers have been designed and fabricated using MOCVD heterostructures. It has been shown that by taking into account the multiple reflections at the gate load, a very flat gain can be achieved and the sensitivity of the amplifier to the load resistances can be considerably reduced. By suitable design, the frequency bandwidth of the amplifier can be increased above the cutoff frequency of the active devices. In particular, it is shown that the cascode configuration reduces the coupling between gate and drain lines and increases the gain-bandwidth product, but can generate oscillations. To verify their design approach, the authors present the results obtained on 2-42 GHz monolithic amplifiers using 0.5 mu m HEMTs.