Patent ID: 7414715

Claim:
A circuit for detecting light scattered from a specimen, the circuit comprising: a photomultiplier tube (PMT) coupled for receiving and converting the light scattered from the specimen into an electrical signal, wherein the PMT comprises a cathode and a plurality of stages consisting of a multitude of dynodes and an anode, wherein the electrical signal is amplified at each successive stage to produce an output signal at the anode stage; means coupled to the PMT for receiving the output signal along with an intermediate signal representing the amplified electrical signal at one of the dynode stages of the PMT, for supplying the output signal along to an inspection system component as long as the output signal remains below a predetermined threshold value, and for supplying the intermediate signal to the inspection system component once the output signal reaches the predetermined threshold value; and a plurality of resistors coupled between the cathode and the anode of the PMT, wherein the plurality of resistors are separated into a first portion of serially-coupled resistors and a second portion of serially-coupled resistors, each having a separate power supply therewith, and wherein the first and second portions are not coupled in series.