| 摘要 |
PURPOSE:To reduce the area of a layout by providing separately a diode MOSFET which detects a boosted voltage being raised above a constant level and a MOSFET which limits the level of the boosted voltage. CONSTITUTION:When the boosted voltage Vpp' is set more than the composite threshold voltage of MOSFETs Q28-Q30 higher than a voltage Vpp, those MOSFETs Q28-Q29 are turned on. Thus, the MOSFET Q28 is turned on to turns on a MOSFET Q31 which is put in current mirror relation with the MOSFET Q29. When the size (W/L) of the MOSFET Q31 is set relatively large, the MOSFET Q31 has large current ability proportional to its size ratio to the MOSFET Q28 and limits the level of the boosted voltage Vpp'. Thus, the one MOSFET limits the level of the boosted voltage Vpp', so the area of the layout is reduced as the whole level limiter circuit.
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