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A fully differential SC bandpass filter (central frequency, 58 kHz; Q= 15; and voltage gain, 8) based on the switched-opamp approach is designed and implemented in this work. The filter operates from a single 1 V supply voltage and is realized in a 0.35 μm CMOS technology. It has been characterized with a sampling frequency of 1 MHz and its power consumption is about 230 μW. As a main internal filter component, an appropiate switched opamp was also designed. Its common-mode feedback circuit was implemented by using an error amplifier and sampling of the output common-mode voltage is carried out by applying a DC offset to level shift the common-mode sample. It provides an accurate common-mode output for a wide temperature and supply voltage ranges.

In this work it is demonstrated conclusively that the capacitance–voltage transient technique can be used to analyse the spatial distribution and to study the electrically enhanced emission phenomena of deep levels in semiconductors. Results obtained using the technique for two types of defect, namely, the damage induced in silicon by boron implantation processes, and the DX centres in silicon doped AIGaAs alloys (the most commonly encountered defects in these materials) are presented. For the boron implanted silicon, the existence of two deep levels with non-homogeneous concentrations located in the lower half of the band gap wasfound. With regard to the DX centres, the experimental data show that these centres do not exhibit electrically enhanced emission rates, at least for the present experimental values of the electric field, in spite of the well established donor nature of these centres. This result can be explained in terms of the characteristic that these levels show thermally activated capturerates.MST/3322