Switching scheme to improve linearity and noise in switched capacitor stage with switched feedback capacitor

摘要

A switch capacitor amplifier using a "bottom plate sampling" type arrangement in the feedback network to mitigate the reduction in linearity due to feedback switch charge injection. The switch ( 18 A) connecting the feedback capacitor (Cf) to the opamp ( 15 ) input is opened prior to the switch ( 19 A) connecting the feedback capacitor (Cf) to the output such that the charge injected into the opamp input nodes come from the switch connected to the opamp input, and is independent of the signal value to the first order as the switches are at the opamp input common mode voltage.