Proposed pulse frequency modulation circuit diagram where a source follower is newly added to digitize a dark current in high speed.

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... is insufficient to promptly process the captured images for high-resolution retinal applications. To overcome this technical limitation, in this study, we devised a high-speed PFM structure by adding a source follower, followed by the photodiode illustrated in Figure 5. The source follower works to increase the voltage-drop speed at VX using Equation (1), which has a non-inverting gain over 1. í µí°´í µí±£ = í µí± í µí±’í µí± í µí±–í µí± í µí±¡í µí±Ží µí±›í µí±í µí±’ í µí±¡í µí±–í µí±’í µí±‘ í µí±í µí±’í µí±¡í µí±¤í µí±’í µí±’í µí±› í µí±†í µí±œí µí±¢í µí±Ÿí µí±í µí±’ í µí±Ží µí±›í µí±‘ í µí°ºí µí±í µí°· 1 í µí±” + í µí± í µí±’í µí± í µí±–í µí± í µí±¡í µí±Ží µí±›í µí±í µí±’ í µí±¡í µí±–í µí±’í µí±‘ í µí±í µí±’í µí±¡í µí±¤í µí±’í µí±’í µí±› í µí±†í µí±œí µí±¢í µí±Ÿí µí±í µí±’ í µí±Ží µí±›í µí±‘ í µí°ºí µí±í µí°· = 1 + í µí±” í µí±” ...