A packaged broad-band monolithic variable gain amplifierimplemented in AlGaAs/GaAs HBT technology

Broad-band amplifiers find application in fiber-optic communication link and instrumentation or serve as generic components in high-speed electronic test laboratories. With an advanced AlGaAs/GaAs heterojunction bipolar transistor (HBT) technology, we have designed and fabricated broad-band monolithic variable gain amplifiers (VGAs). High-speed packages for the VGAs were carefully designed to minimize insertion and return losses and to suppress undesired package cavity resonances. Accurate and efficient models for the packages were obtained based on experimental data so that their parasitic effects could be considered in the VGA design. The packaged VGAs provided 10-16 dB adjustable gain with approximately ±1 dB gain variations and constant group delay in the DC-26 GHz band, and showed better than 10 dB input/output return losses in the amplifier passband. When the packaged VGAs were inserted in a 30 Gb/s electronic link, error-free operation was achieved for a 2³¹-1 input pseudorandom bit sequence. These VGAs can be used in fiber-optic transmission systems with data rates up to 30 Gb/s