| 摘要 |
PURPOSE:To obtain the analog voltage in a wide range between zero and the power supply voltage level by using both nMOS and pMOS transistors to form a gate transistor which is switched by the digital input. CONSTITUTION:A pMOS transistor TR is used to a TR for a selection switch 21; while an nMOS TR is used to the other selection switch 22. The pMOS TR is turned on when its source potential is higher than its gate potential. While the nMOS TR is turned on when its source potential is lower than its gate potential respectively. Thus a gate can be driven at a level lower than the power supply potential. Furthermore an analog switch 23 uses a CMOS transfer gate and can lead completely the potentials ranging from zero through the power supply voltage level to an output line 18.
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