Omnivision patent application US20120153123 presents dual conversion gain pixel with a possibility of FD voltage boost. A prior art dual conversion gain pixel just adds a cap on FD like this:
Omnivision proposes to connect the cap from outside of the array, like that:
The low CG setting can be made even lower by adding -G amp, like shown below:
Once we are at column amplifiers, one obvious improvement is to add a positive gain amp for the high CG setting, so that the effective FD capacitance would be reduced by a weak positive feedback. For some reason the application does not mention this option.
The added capacitor also allows to boost FD potential to (over)compensate the charge injection and control feedthrough when RST gate turns off (the first figure is prior art, the second one is improvement):
Omnivision proposes to connect the cap from outside of the array, like that:
The low CG setting can be made even lower by adding -G amp, like shown below:
Once we are at column amplifiers, one obvious improvement is to add a positive gain amp for the high CG setting, so that the effective FD capacitance would be reduced by a weak positive feedback. For some reason the application does not mention this option.
The added capacitor also allows to boost FD potential to (over)compensate the charge injection and control feedthrough when RST gate turns off (the first figure is prior art, the second one is improvement):
