A circuit includes a first amplifier and a second amplifier, wherein first amplifier is configured to receive an input current at a first input of the first amplifier, and an output of the first op-mp is configured to drive a first input of the second amplifier. The filter includes resistance elements; capacitance elements, each of which consists of a capacitance-value switching circuit that can vary the capacitance value of the capacitance element; and operational amplifiers. An inventive wafer handling method which divides a lot of wafers into sublots and distributes the sublots among tools configured to perform the same process is also provided.