An integrated photodetector-amplifier using a-Si p-i-n photodiodes and poly-Si thin-film transistors

The authors propose a photodetector-amplifier circuit consisting of a bridge photodetector circuit and a CMOS differential amplifier, both monolithically integrated on a transparent substrate. A test circuit was fabricated using a-Si p-i-n photodiodes and poly-Si thin-film transistors on a quartz substrate. A clear effect of the differential amplifier was demonstrated in the test circuit. It is shown that the circuit performance can be controlled by changing the bias current of the differential amplifier. With a relatively low bias current on the order of 10/sup -11/ A, the circuit works digitally with output voltages either close to 0 V or V/sub DD/. The power consumption of the circuit is approximately 60 mu W, which is low enough for use in two-dimensional arrays.<>