Bandwidth broadening of the photodetector signal path

The paper addresses bandwidth widening of an analog signal path, composed of a high-speed infrared photodetector, an amplifier and a transmission line connecting the two. To investigate influence of design variables upon bandwidth a simplified model of the signal path is analyzed first. Several design scenarios are considered, including transmission line length adjustment, but also insertion of a simple LC corrector. Trade-offs between bandwidth and pass-band ripple level are revealed numerically, also for a realistic model of an infrared photodetector, wide band gain-block and a flexible strip line connection. It is shown that the simple T-corrector can result in substantial bandwidth increase. Interestingly enough, in most cases tested similar broadening can be provided by appropriate tuning of the connection line length only.