Abstract: An ambient light sensor includes a substrate, a buffer layer formed on the substrate, an absorption layer formed on the buffer layer for absorbing the visible light, and a filter layer formed on the absorption layer for filtering infrared light and high-energy photon insensitive to human eye. The absorption layer is a PIN junction having a compositional graded intrinsic layer. The peak wavelength of responsivity spectrum of the ambient light sensor is very close to that of human eye.

Abstract: There is provided an ambient light photodetector, comprising a substrate, and a buffer layer formed on the substrate, an absorption layer represented by AlxGa1?xAs where 0<×<1, formed on the buffer layer used for absorbing visible light; and a filter layer made of GaAs, formed on the absorption layer used for absorbing light between 300 nm-860 nm. Such an eye-like photodetector has a spectral response which corresponds to that of the human eye.

Abstract: The invention proposes a lumped constant compensated high/pass balun (balance line to unbalance line transition). The proposed circuit can be used in microwave integrated circuit(MIC) and mononolithic microwave integrated circuit(MMIC) designs. The basic operating principle of the proposed circuit is to use two sets of lumped type high pass and low pass filters to synthesize a microwave balun. The first filter set provides the wide band 180.degree. phase difference property for the balun circuit. The amplitude imbalance of the balun is compensated by the other filter set. The advantage of the proposed circuit is to replace the bulky and non-planar distributed balun or traditional transformer in low microwave frequency range.