This thesis proposes a dB-linear programmable variable gain amplifier (VGA) and a voltage peak detector with digital calibration for FPW-based antibody sensing system. In the first topic, a dB-linear programmable variable gain amplifier is proposed. By using two source followers as the input terminals, input signals with very low DC offset could be received. The linear local-feedback transconductors are employed to be trans-condurctor-stage and load-stage. Besides, a reconfiguration method is used to reduce the layout area and improve the linearity of the gain to attain gain error less than 0.86 dB measured on silicon. In the second topic, a voltage peak detector with digital calibration is proposed. The voltage peak of the input sine-wave signal is sampled and held by using an integra-tor, a digital-to-analog converter, and a voltage comparator to generate a square-wave signal. Besides, the voltage error caused by the propagation delay could be calibrated by the proposed digital calibration method. The frequency of input signal is up to 20 MHz and the voltage error is justified to be less than 0.81 % by simulations.

[Truncated abstract] This study describes the results of a four and a half year investigation examining local regulation of ion transport through pumping epithelial cells. The study focussed on the standard isolated toad skin preparation, made famous by Hans Ussing. Originally, the objective was to perform some simple manipulations on the isolated toad skin, a standard and well-tested epithelial layer, which, according to the literature, was a well-behaved and stable preparation. The purpose of doing these toad skin experiments was to gain familiarity with the experimental techniques, such as measuring the open-circuit voltage (Voc) and the short-circuit current (Isc) across an epithelium. In the process, the experimental information that was obtained was to assist in the development and refinement of a mathematical model of a single pumping epithelial cell . . . Finally, it should be emphasised the toad skin was a convenient tissue model for exploring more general issues such as: (i) how pumping epithelial cells may adjust to changes in the extracellular environment by locally regulating their membrane conductances; (2) how the topology of a cell can influence its function (i.e. the topology can determine whether a cell is optimised for salt transport or water transport). (3) how different cells, with different functions, may be positioned in apposition in a pumping epithelial tissue so that gradients generated by one cell type can be utilised by another. From a broader perspective, it is likely that such issues are also applicable to other pumping epithelia, and ultimately, may assist in understanding how these epithelia function.