Patent ID: 8203111

Claim:
CMOS image sensor comprising: at least one current source for generating a predetermined signal current on a signal line; and a first pixel including: at least one photodiode connected between a first voltage source and first node; a select transistor having a first terminal connected to the signal line and a second terminal connected to a second node; a reset transistor having a first terminal connected to the first node and a second terminal connected to the second node such that a signal path is formed between the signal line and the at least one photodiode through the select transistor and the reset transistor during a reset operation, and a charge amplifier coupled between the first node and the second node, the charge amplifier having a common source configuration arranged such that a charge generated by the at least one photodiode is amplified by the charge amplifier and transmitted onto the signal line, wherein the charge amplifier comprises an NMOS charge amplifier transistor having a first terminal connected to the second node, a second terminal connected to the first voltage source, and a gate terminal coupled to the first node, wherein the first pixel further comprises a transfer transistor connected between the at least one photodiode and the first node, wherein the first pixel further comprises a pull-up transistor connected between a second voltage source and the gate terminal of the NMOS charge amplifier transistor, and wherein the CMOS image sensor further comprises means for turning on the pull-up transistor when said select transistor is turned off, whereby the pull-up transistor prevents leakage through the transfer transistor during an integration period by generating negative gate-to-source voltage on the transfer transistor during the integration period.