Patent ID: 7642770

Claim:
A light-driving circuit, suited for measuring of a plurality of grounded probes of a test instrument and comprising: a light emission device for emitting a light in response to a control signal; a power detection device for detecting a power of the light to generate a working voltage signal; a comparator having a first input for receiving a reference voltage signal, a second input for receiving the working voltage signal, a ground node electrically connected to a ground pad, and an output depending upon a signal comparison between values of the working and reference voltage signals, generating a deciding signal; and a feedback circuit electrically connected to the output of the comparator, according to the deciding signal, providing the control signal to adjust the light power of the light emission device, wherein when the ground pad is located on a surface of a die and simultaneously connects the plurality of grounded probes, the connections among the ground pad and the grounded probes produce parallel probing resistances and establish multiple grounding paths.