Low-noise optimisation of current-mode transimpedance optical preamplifiers

Techniques for minimizing the noise performance of current-mode common-gate and common-base optical transimpedance preamplifiers are presented. For common-gate input preamplifiers, it is shown that the size of the input FETs can be chosen to achieve the minimum possible noise performance. Both theoretical analysis and simulated results using 30-GHz GaAs MESFET technology confirm the concept. Modified simpler designs for both common-gate and common-base similar low-noise properties are described. Simulated results using GaAs heterojunction bipolar transistor (HBT) and MESFET technology demonstrate that almost 2 dB lower electrical noise performance (compared with classical voltage-mode designs at a 10 GHz bandwidth) can be obtained with the new topologies. In both cases, the transimpedance gain is at least a factor of 4 higher than that obtained with classical counterparts. Preliminary measured results of the GaAs HBT preamplifier are presented