A CURRENT SOURCE WITH IMMUNITY FROM IR-DROP FOR HIGH-RESOLUTION CMOS IMAGE SENSORS
A current source circuit for high-resolution CMOS image sensors is introduced in this paper, which can provide a stable current with immunity from IR-drop along the power and ground wires. In the circuit, two pre-charged oating capacitors controlled by two-phase non-overlap clock are connected between the gate and source of a MOS transistor alternately to maintain a constant VGS of the MOS transistor. In this way, the current owing through the MOS transistor will be stable and has nothing to do with power level. The post simulation results show that the current supplied by the proposed circuit decreases only by 1.6% when the voltage of the power supply decreases by 30%. The simulations have proved that the proposed circuit can improve the performance of high-resolution CMOS image sensors.
current source ir-drop high-resolution cmos image sensor parasitic resistance