Research On The Design Of Trans-impedance Filters

The quick development of Internet of Things and various testing equipmentsrequire high precision for weak signals. The traditional voltage mode filter canprocess the voltage signal perfectly, but it will encounter many problems if applied tocurrent signal directly, which is the output signals for sensors. It needs a new kind offilter, whose input is current signal and output is voltage signal. As its dimension isimpedance, this kind of filter is called trans-impedance filter.Based on the design of general voltage-voltage filters, the common method ofdesign trans-impedance filters is transforming the voltage source into current source,according to source transformation of circuit theory. This method is calledDirect-Conversion method, which is applicable to some filter circuits. But for mostbiquad filter circuits whose input ports are complex or structures are unusual, as aresult, source transform can not be applied. In this paper, several methods fortrans-impedance filter design have been proposed, such as Parallel-Grounding method,Circuit-Compensation method etc. By adding or removing certain components, orchanging the topology of circuits, trans-impedance filter biquad circuits can berealized. Besides, some new circuits of trans-impedance filters are found on the basisof existing achievements, and characteristics simulation and parameters calculation ofthese circuits are performed for low-pass, band-pass, band-stop and high-pass. So itcan be used for trans-impedance filter design directly.The main innovation of this paper is the proposition of several new methods for thedesign of trans-impedance filters. The methods of Parallel-Grounding andCircuit-Compensation are applicable to filters with certain structures up to now. Incontrast, from the symbolic transfer function to find trans-impedance circuit is morecommonly used, and could be applied to find new trans-impedance filter circuits, andsome examples are given and their feasibility has been verified.