60 GHz-bandwidth distributed baseband amplifier IC in a package optimized for isolation

A wideband amplifier operating from dc is indispensable for waveform processing such as data signal amplification in optical transmission systems. There are two serious problems in widening the bandwidth of the amplifier IC. One is the chip mounting, where the wavelength of the electrical signal approaches the physical size of the mounting elements such as the package cavity, input/output leads, bonding wires and so on. Therefore, the three-dimensional distributed effects of these elements must be controlled in the circuit design for stable amplifier operations. The other is the circuit configuration of the amplifier. Amplifiers designed using the lumped-constant theory have a bandwidth restriction caused from parasitic capacitance. On the other hand, a distributed amplifier is capable of eliminating this restriction. A suitable package is based on the concept of "a chip-size cavity package", by which the parasitic resonance is suppressed and the isolation characteristics between input and output ports are greatly improved. Second, a frequency-dependent biasing termination is employed for the drain-line of the amplifier to improve gain degradation at frequencies below 1OGHz.<>