| 摘要 |
PURPOSE:To enable the accurate measurement of a threshold voltage of an N- channel MOS element by connecting a drain and a gate particularly in such a manner that the drain is connected to a first outside terminal with low impedance and a source to a second outside terminal with low impedance. CONSTITUTION:FETQ3 for measuring Vth is attached to NMOSRAM of a 5-V single power source, and connected to an output terminal T31 and a VCC terminal T32 in a prescribed manner. When a positive voltage VT31>VT32+Vth is impressed on the terminal T31, FETQ3 is turned ON, and the correlation between the operation parameter of RAM and Vth can be measured as it is, without any hindrance to the proper function of RAM. When T33 serves as an address input terminal, an input to RAM is prepared by T<2>L, etc., and a standard DC voltage value is not impressed thereon in normal operations. Therfore, the proper operations of RAM are not affected adversely even when an impression causes leakage between the terminals T31 and T32. That is, according to AC standards, except DC standards, no hindrance is caused whatever input or output terminal serves as T31. Vth thus obtained is effective for specifying the state of parasitic MOS in the conditions of employment, and is useful for checking the dynamic characteristic of the entire device wherein N-channel MOSFET is employed. |
