| 摘要 |
PROBLEM TO BE SOLVED: To provide an input protection circuit capable of miniaturizing a device itself, and preventing saturation of a signal processing circuit in which an input is in the open state. SOLUTION: In this input protection device of an LSI test system, plural measuring circuits are connected to output pins of a large scale integrated circuit which is a test object, and an output signal of the output pin is selectively inputted into the measuring circuit corresponding to a test purpose. The device is equipped with a switch circuit inserted in a signal input route of the measuring circuit, for selectively inputting the output signal of the output pin into the measuring circuit by a signal switching signal, a clamp circuit for applying a clamp voltage on the signal input route of the measuring circuit through a diode, and a clamp voltage switching part for executing voltage switching of the clamp voltage. The device is constituted so that the clamp voltage switching part applies the clamp voltage required for input protection on the clamp circuit of a signal input route from which the output signal of the output pin is inputted into the measuring circuit and applies the clamp voltage for avoiding saturation of an input potential of the measuring circuit on the clamp circuit of a signal route in which the output signal of the output pin of the LSI is cut off.
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