| 摘要 |
PURPOSE:To attain several kinds of different characteristics tests without destroying a measuring circuit even if the voltage to be applied to an terminal to be measured is changed by using the measuring circuit following the output level of an object to be measured. CONSTITUTION:Operational amplifiers 1 and 2 are actuated only when current is made to flow in from an object 6 to be measured to a measuring circuit by a diode 4 and when current is made to flow out from the measuring circuit by a diode 5 respectively and the voltage[electric potential at point (a)]to be applied at that time coincides with the potential of an input of the positive side of the amplifier 1 or 2. When the output level of the object 6 to be measured resides between VRH and VRL, the measuring circuit observed from the object 6 is in high impedance (equivalently turned off) because a feedback loop between both the amplifiers 1, 2 is interrupted by the disconnected diodes 4, 5. Consequently the object 6 to be measured and the measuring circuit are prevented from excess current. |
