An imaging device may have an array of image sensor pixels each having a photodiode and a floating diffusion node. Each image sensor pixel in the array may also include a dual conversion gain switch and a dual conversion gain capacitor that allows the image sensor pixel to operate in a low conversion gain mode during which the switch is turned on to share charge between the floating diffusion node and the dual conversion gain capacitor, and a high conversion gain mode in which the switch is turned off. During integration, the photodiode may generate more charge than can be held at the floating diffusion node. A buried channel may be provided beneath the dual conversion gain switch to provide a path along which the excess charge can be shared between the floating diffusion node and the dual conversion gain capacitor even when the dual conversion gain switch is off.