presented in this paper aims at combining these two modes of operation in order to enable the fabrication of selfpowered
optical sensor systems. The ability of CMOS processes with a feature size of 0.35 μm and smaller to be
operated using a supply voltage at 1V is an essential enabling factor for this concept. The reduced power supply
voltage with reduced feature size is usually considered a disadvantage in analog circuit design, as it reduces the
dynamic range at a given noise level. However, it does enable direct electrical powering of the circuit from a set of
two photodiodes.
The operating principle as compared with the conventional sun sensor is described in detail in the next part. The
chip with photodiodes and current-to-voltage converter is designed and implemented. The experimental result shows
the differential current between photodiodes can reflect the shadow imposed on photodiode where a needle is on top
of chip. Conclusions are drawn in the final section along with an outline of future work.