| 摘要 |
PURPOSE:To measure a current with high precision by providing a detecting circuit for a current flowing to a specific pin in a test head. CONSTITUTION:The test head 20 is provided with the current detecting circuit 21 and the output of a booster 13 is connected to a connection terminal 22 for an IC pin through a cable 30 and the circuit 21. Measurement ranges of the circuit 21 can be switched and its measurement range is set from the side of a test station 10. An operational amplifier 23 feeds the potential at the terminal 22 back to an operational amplifier 12 with low impedance and its output and an inversion-side input are coupled together, so that the amplifier operates as a buffer. The uninverted input terminal of the amplifier 23 is coupled with the terminal 22 and its output is coupled with the inversion side input of the amplifier 12 through a resistance 14. The inversion-side input is connected to the output of a D/A converter 11 through a resistance 14 as well. Therefore, the potential at the terminal 22 varies following up the output potential of the converter 11 and has the different polarity and the ratio of absolute values of both potentials is determined depending upon the ratio of resistance values of the resistances 14 and 15.
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