Abstract: A digital image sensor includes a sensor array of digital pixels which output digital signals as pixel data. Each of the digital pixels includes a photodetector producing an analog signal indicative of the amount of light impinging on the sensor array and a charge transfer amplifier coupled to receive the analog signal and generate an amplified pixel voltage signal. The digital image sensor further includes analog-to-digital conversion (ADC) circuits located within the sensor array. Each of the ADC circuits is connected to one or more charge transfer amplifiers of the digital pixels for converting the amplified pixel voltage signal of each digital pixel to a digitized pixel voltage signal. The charge transfer amplifier operates to increase the sensitivity of the digital image sensor. The charge transfer amplifier can be implemented as a transfer gate with a floating diffusion as a measuring capacitor.

Abstract: A circuit includes an analog-to-digital (A/D) converter for multiplexing between a number of analog input signals and converting the selected analog input signals to a digital code representation. The A/D converter includes a comparator having a first input terminal connected to receive the first signal having a number of levels, a second input terminal connected to receive a multiple number of analog input signals, and a third input terminal for receiving a multiple number of input select signals. The comparator includes a multiplexer coupling the multiple number of analog input signals to a multiple number of corresponding input signal paths. The multiplexer selects one of the multiple number of input signal paths based on the multiple number of input select signals. In one embodiment, the A/D converter is applied in a digital image sensor for performing pixel-level analog-to-digital conversion using a multi-channel bit serial ADC technique.