Patent ID: 8502549

Claim:
A test apparatus for judging pass/fail of a device under test depending on a load voltage or a load current supplied to the device under test, the test apparatus comprising: a driver circuit that supplies, to the device under test, a test signal corresponding to an input signal; and a judging section that judges pass/fail of the device under test, the judgment based on one of the load voltage and the load current, the load voltage supplied to the device under test when the test signal has a predetermined current, the load current supplied to the device under test when the test signal has a predetermined voltage: wherein the driver circuit includes: a driver section that outputs the test signal and selects a voltage of the test signal according to the input signal, from among a plurality of voltages supplied to the driver section, the driver section including a buffer that supplies a supply current to the device under test from a high voltage power-source line, and draws a draw current from the device under test into a low voltage power-source line, the buffer including: a high voltage transistor having a first collector terminal electrically connected to the high voltage power-source line, and a first emitter terminal electrically connected to the device under test through which the test signal is outputted, and a low voltage transistor having a second emitter terminal electrically connected to the first emitter terminal, and a second collector terminal electrically connected to the low voltage power-source line, a supply current detecting section that detects the supply current, the supply current detecting section including: a high-voltage-side detecting section provided between the high voltage power-source line and the high voltage transistor, and detects a high voltage current of the first collector, and a low-voltage-side detecting section provided between the low voltage power-source line and the low voltage transistor, and detects a low voltage current of the second collector, a base current detecting section that detects a high voltage base current of the high voltage transistor and a low voltage base current of the low voltage transistor, and an output control section that controls one of a voltage and a current of the test signal based on the supply current detected by the supply current detecting section, and controls the plurality of voltages so that a difference between a high emitter current and a low emitter current becomes a predetermined constant current, the high emitter current obtained as a summation of the high voltage current and the high voltage base current, and the low emitter current obtained as a summation of the low voltage current and the low voltage base current.