| 摘要 |
PURPOSE:To prevent latchup by setting a threshold voltage of a P-channel MOS transistor(TR) of a CMOS circuit so as to satisfy a specific condition. CONSTITUTION:When an absolute value of a threshold voltage Vthp of a P- channel MOS TR 2 is smaller than 0.7V being a forward on-voltage of the pn junction, a channel layer is formed to the TR 2 before the pn junction is conductive and a current I1 flows from a drain DP of the TR 2 to a source SP. Thus, the drain DP of the P-channel MOS TR 2 is clamped to a level Vc+ Vthp, the pn junction is not conductive thereby preventing a parasitic bipolar TR QA from being turned on. That is, since the TR QA is not turned on, no latchup is induced. Thus, the absolute value of the threshold voltage Vthp of the P-channel MOS TR 2 connecting to an external terminal is made lower than the voltage 0.7V where the pn junction is conductive in the wafer process stage to prevent easily latchup. |
