| 摘要 |
There is provided a low charge-injection charge pump for supplying charge into a charge summing node to generate a low noise output voltage. The charge pump includes a PMOS current source coupled between a first PMOS switch and a charge summing node. The charge pump also has a NMOS current source coupled between a first NMOS switch and the charge summing node. The switches operate to turn ON the current sources to allow charge to flow into, or out of, the charge summing node to increase or decrease the voltage present on the charge summing node. The positioning of the switches away from the charge summing node serves to prevent channel charges in the first PMOS switch and in the first NMOS switch from flowing into the charge summing node when either of the two switches are turned OFF. Furthermore, a second PMOS switch and a second NMOS switch are employed to dissipate channel charges flowing from the channels of the first PMOS and NMOS switches when those switches are turned OFF. The second PMOS and NMOS switches also operate to bias the PMOS and NMOS current sources so that they do not conduct when the first PMOS and NMOS switches are turned OFF. The dissipation of channel charge and the biasing of the current sources operate to reduce noise on the charge summing node.
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