A fast sample and hold charge-sensing circuit for photodiode arrays

An on-chip charge-sensing circuit with a feedback loop has been designed for improving the charge-transfer speed in photodiode arrays. Its large output voltage swing combined with improved speed performances, makes this circuit well-suited for OCR applications, especially low-cost data capture devices. Sample and hold operation can easily be performed without increasing the Si real estate, making parallel output feasible with frame rates of 3 kHz for arrays with 500 pixels. Experimental arrays were built in standard p-channel aluminum-gate technology.