Patent ID: 7521937

Claim:
A measurement circuit that applies a predetermined direct voltage to a device under test and measures a direct current flowing into the device under test, the measurement circuit comprising: a main amplifier that generates the direct voltage in accordance with an input voltage and applies the generated voltage to the device under test; a feedback element that feeds back the direct voltage to the main amplifier and controls the direct voltage generated from the main amplifier to a voltage according to the input voltage; a current detecting circuit that outputs a detecting voltage according to a current value of the direct current; and a clamping circuit that restricts the current value of the direct current output from the main amplifier, and the clamping circuit comprising: a first limiting-voltage output section that outputs a limiting voltage according to a limiting value of the direct current; a first bias generating section that generates a bias voltage making use of the input voltage as a reference voltage based on a magnitude relation between the limiting voltage and the detecting voltage; and a limiting-current supplying element that is provided between a connecting point between the main amplifier and the feedback element and the first bias generating section and supplies a limiting current restricting the direct current to the device under test via the feedback element in accordance with a voltage difference between a voltage in the connecting point and the bias voltage.