Patent attributes
A pixel cell with increased dynamic range is formed by providing a floating diffusion region having a variable capacitance, controlled by at least one gate having source and drain regions commonly connected to the floating diffusion region. The gate has an intrinsic capacitance which, when the gate is activated, is added to the capacitance of the floating diffusion region, providing a low conversion gain readout. When the gate is off, the floating diffusion region capacitance is minimized, providing a high conversion gain readout. The gate may also be selectively switched to mid-level. At mid-level, a mid-level conversion gain, which is between the high and low conversion gains, readout is provided, but the gate still provides some capacitance to prevent the floating diffusion region from saturating.
