Patent ID: 8040124

Claim:
An apparatus for monitoring leakage current of a Faraday cup in an ion implanter, comprising: an operation amplifier, wherein an output of said operation amplifier is electrically coupled with an inverting input of said operation amplifier through a resistor; and a current branch circuit, wherein said current branch circuit is selectively coupled to the Faraday cup, and wherein the current branch circuit has a first terminal, a second terminal, a first node and a second node, said first terminal and said second terminal being separately electrically coupled with two voltage sources, each voltage source having an equal magnitude and opposite polarity, said first node being located between and electrically coupled to said first and second terminals, and electrically coupled with a current output of said Faraday cup, and said second node being located between and electrically coupled to said first node and said second terminal and electrically coupled with said inverting input of said operation amplifier, wherein the Faraday cup and the operational amplifier and current branch circuit comprise a portion of the ion implanter.