| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 99 === Abstract
The precision of a output signal, making sure the signal is in or between the programed frequency band, is very important and top priority in analog filter circuit design field. To catch the subtle signal such as human body’s physiology by cardiograph, the precision is very important but often affected by test environment and facility itself. Therefore, the precision of the filter design is a crucial topic for research.
OTA (Operational Transconductaance Amplifier) is best candidate for analog filter circuit design identified by savants recently. The main character of OTA is , where Io stands for output current, stands for positive input voltage, stands for negative input voltage, stands for trans-conductance value, and the input current I+=I-=0.The trans-conductance of OTA, it is the ration of output current ( ) and input voltage diviation , can be adjusted and controlled by bias current ( ).Some savants proposed the analytical synthesis of OTA-C circuit, which has some advantages like (1) controllable (2) a wide band of operation frequency (3) high input impedance (easy to cascade other circuit) (4) to minimize component counts (can decrease parasitical effect to minimum for raising the precision of the signal in circuit)
The realization of circuit design in thise thesis, was based on the method of analytical synthesis,node analysis and transfer function represented by matrix. And decompose transfer function into three equations for simplifying circuit building. Finally, to combine those three circuits for completing whole elliptic filter circuit.
With the advantage of node analysis to design the current-mode fourth-order elliptic low pass filter, we can have minimum component usage. Therefore, only few OTAs and capacitors can realize a 57Hz low pass filter. Before building the circuit, the simulations were based on the results of H-Spice and Matlab, and then to choose LM13700 (National Semiconductor Corp.) for OTA design selection. Finally, the connection between theoretics and experiment of proposed elliptic low pass filter were been proofed in this thesis. We hope it can be a valuable reference for those who join the research of elliptic filter afterward.
Finally, this is designed of the 57Hz low-pass elliptic filter circuit, looking off the assembly line actually made of integrated circuits for use in the actual being in the electrocardiogram apparatus.
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