Broadband GaAs monolithic equalizing amplifiers for multigigabit-per-second optical receivers

A preamplifier IC, a gain-controllable IC, and main amplifier ICs with and without three-way dividers for multigigabit-per-second optical receivers have been developed using a single-end feedback circuit, two peaking techniques, and advanced GaAs process technology. The preamplifier circuit is implemented in two stages, each consisting of a common source circuit with a source follower. The output impedance matching is realized with a common source circuit. To obtain wide bandwidth and optimize the input impedance and noise characteristics, parallel feedback was applied. The gain-controllable amplifier adopts basically the same configuration as the preamplifier. The output of the main amplifier must be divided among decision, timing, and gain-controller circuits. Amplifiers with a three-way divider applying resistors and FETs have been studied. The amplifier ICs were fabricated by advanced SAINT (self-aligned implantation for N/sup +/-layer technology) process. These ICs have a 3-dB bandwidth of more than 5 GHz and can be applied to optical receivers transmitting NRZ (nonreturn to zero) signals in excess of 7 Gb/s. Performance results for the circuits are presented.<>