Patent ID: 7109463

Claim:
An amplifier circuit having a photomultiplier tube comprising a photocathode; an anode; a plurality of dynodes interconnected with one another and between the photocathode and the anode so that an output of one dynode provides an input to a next dynode within the photomultiplier tube; and a switching device having a first terminal coupled to an output of a constant current source and a second terminal operable to be selectively coupled to a respective output of any of the dynodes coupled between the photocathode and the anode such that an amplifier circuit output current representing a difference between an output of the constant current source and an output of a selected one of the dynodes is generated by the switching device switching the output between any one or more of the dynodes and the switching device switches between a respective dynode output current dependent upon a time period that an output current from the anode is in a saturated state.