High-Speed, High Dynamic-Range Optical Sensor Arrays

A monolithic solid-state linear sensor array has been designed and fabricated in a 0.35 mu m, 3.3 V, thin-oxide digital CMOS process. The sensor arrays are targetted at such instruments and applications as digital streak cameras, 2-D cameras for proton radiography, and fiber-optic array readout. The prototype consists of a I-D linear array of 150 integrated photodiodes, followed by fast analog buffers and on-chip, 150-deep analog frame storage. Frame storage consists of 150 analog sample circuits per pixel, with each sample circuit including an n-channel sample switch, a 0.1 pF double- polysilicon sample capacitor, a reset switch to clear the capacitor, and a multiplexed source-follower readout buffer. Sampling speeds of 400 M-frames/s have been achieved using electrical input signals, and 100 MHz with optical input signals, both with a dynamic range of similar to 11.5 bits, rms. Circuit design details are presented, along with the results of electrical measurements and optical experiments with fast pulsed laser light sources at several wavelengths. A set of next-generation concept designs are also presented that aims to include PLL-based clock multiplication for 1 GHz continuous sampling, plus a new real-time trigger circuit technique that examines windowed regions of stored samples to form a sophisticated trigger decision.