Method to eliminate bus voltage drop effects for pixel source follower amplifiers

摘要

A CMOS image sensor includes an array of pixels; a plurality of buses, and each bus is connected to a portion of the pixels, each pixel includes (a1) a photodiode for capturing incident light and converting the light to charge packets; (a2) a source follower amplifier that receives a signal from the photodiode and functions as voltage buffer to drive the photodiode signal across the bus; the image sensor also includes a readout circuit for receiving and storing the output voltage from the amplifier; a current source electrically connected at an opposite end of the bus from the readout circuit to provide a bias current for the source follower amplifier so that there is no current-resistance voltage drop error due to the bias current and bus resistance at the readout circuit.