Patent ID: 7141984

Claim:
A switching circuit for range resistors for current measurement, the switching circuit comprising: at least two first semiconductor switches, each having a first input portion, a second input portion, and an output portion and being capable of switching a connection between the first input portion and the second input portion; range resistors provided between a device under test and the respective output portions of the at least two first semiconductor switches, the range resistors having different resistances from each other; a second semiconductor switch having at least two input portions and an output portion, the input portions of the second semiconductor switch being connected to the output portions of the at least two first semiconductor switches; a differential amplifier having an input portion connected to the output portion of the second semiconductor switch and an input portion connected to first ends of the range resistors, the first ends being adjacent to the device under test; a voltage source that applies a reference voltage to the first input portions; and wires that connect the second input portions and the first ends of the range resistors, wherein a desired one of the at least two first semiconductor switches which is connected to a desired one of the range resistors is connected to the first input portion and another one of the at least two first semiconductor switches is connected to the second input portion, and the second semiconductor switch is connected to the output portion of the desired first semiconductor switch.