| 摘要 |
PURPOSE:To execute the pre-charge of a half level at a high speed by connecting the drain edge of a pair of FETs, which are serially connected, to distributed capacity together with the gate of the FET in a source edge side and obtaining a circuit constant, with which the source side FET goes to be non-saturated in the initial period of a pre-charge start. CONSTITUTION:For FETs 11 and 12, a gain coefficient beta and a threshold voltage VT are at a same degree. Then, in the initial period, a potential of a terminal B is VB=0 and the FET11 is turned off. Then, the FET12 is turned on and a potential of a terminal A is VA=VDD. When a control signal phi is changed to 0V, the FET11 is turned on and a charging is started to capacity 13. When the gain coefficient and threshold voltage of the FET are obtained at the same degree, in the initial period of the charging, a power source voltage VDD is pressure-divided and the FET12 goes to a non-saturated condition. Then, since a VDS12 goes to be smaller, a VGS11 of the FET11 can be increased more than a conventional circuit and a high speed charging can be executed with a large charging current. Then, the VB rises up and in the condition of VDD-VT, VGS12= VT is obtained. Then, the FET12 is turned off and the charging is ended. |
