Driver circuit apparatus, measuring circuit apparatus and amplifier circuit apparatus therefor

摘要

In known control loops to control a bias current of a laser device, the presence of a parasitic current drawn by an operational amplifier (114) of a monitoring circuit (100) introduces inaccuracies into measurements of mean power output of the laser device. The present invention provides the operational amplifier with an input stage (200) comprising MOSFETs (208, 210), thereby obviating the parasitic current.