The Study Of Modified Current Conveyors And Continuous-Time Filter

In recent years, fully integrated current-mode continuous-time filters have become oneof the several research fields where analog VLSI technologies have obtained significantachievements. The study on related circuits and design methods and its applications are afront subject in microelectronics, circuits and systems. Current-mode continuous-timefilters have drawn great attentions for their important feature of wide bandwidth, highspeed, large dynamic range, good linearity, low power consumption, low operatingvoltage and simple topologies. It also has a broad application prospect intelecommunication, video signal processing, electronic measure, etc. Research works inthis dissertation is started after a fully investigation on the research results given by bothabroad and domestic researchers. The lacks of the performance of second-generationcurrent conveyor (CCII) and the challenges of the design of the fully integratedcontinuous-time filters based on the CCII are analyzed. Theory and technologies fordesigning and implementing current-mode continuous-time filters and improved circuitsof second-generation current conveyor (CCII) are studied systematically. The mainachievements consist of following several aspects:1. A CMOS MOCCII circuit with simple structure and low operation voltage andhigh accuracy is studiedBy optimizing the parameter of the circuits, the studied CMOS CCII circuit is has asimple structure, a low operation voltage and a high accuracy, and a MOCCII is designedby using the basic current mirrors and the CCII. Simulation with TSMC 0.35-μm CMOStechnologies process to the proposed circuit when the power voltage is±1.5V isimplemented, the voltage tracking bandwidth is 112MHz (-3dB) and The current trackingbandwidth is 75MHz (-3dB). The current tracking error of the inverting terminal andnon-inverting terminal is equal to 0.02 in the 75MHz. Good performance comes from thelower input resistance X-terminal.2. A novel CMOS ECCII circuit is proposed based on the current-amplifier A new CMOS high-performance electronically tunable second-generation currentconveyor (ECCII) is presented based on the current-amplifier. The current gain of theproposed ECCII can be controlled electronically by adjusting the ratio of dc bias currentsof the ECCII. Simulation results with TSMC 0.35-μm CMOS technologies process whenthe power voltage is±1.2V shows: the voltage tracking bandwidth is 85 MHz (-3dB) andthe current tracking bandwidth is 61 MHz (-3dB) and Current-gain(k) is 2.4.Current-gain(k) is improved clearly.3. The design theory and method of current-mode second-order filters isresearchedBy optimizing the structure of the circuits, a KHN current-mode filter, current-modefilters with a single input multiple outputs, current-mode filters with multiple inputsmultiple outputs and universal biquadratic filter with equal capacitance and equalresistance based on ASM method are proposed:(1) The KHN current-mode based on MOCCIIs is studied. Filtering circuit is composedof three MOCCIIs and six RC elements. It can realize low-pass, band-pass and high-passfilter outputs at one time. Its passive sensitivity is very low. Compared with the proposeduniversal voltage-mode KHN filters, the composed circuit has a simpler structure andlower number of components.(2) The proposed universal current-mode biquadratic filter with multiple inputs multipleoutputs based on MOCCIIs can realize low-pass, band-pass, high-pass, band-stop andall-pass filtering outputs simultaneously. Filtering circuit is composed of two MOCCIIsand four RC elements. The circuit has the advantage of not any matching among the inputcurrents and passive components, in which is very important to filter integration.(3) A novel current-mode biquadratic filter synthesis method with equal capacitanceand equal resistance based on ASM method is proposed. The proposed synthesis methodis based on the analytical solution of a biquad filter transfer function and the generation ofrealizable transfer functions implemented using lossless integrators. The filter circuitcontains four active elements and eight grounded passive elements, and can realize all fivedifferent generic filtering (LP, BP, HP, BR, and AP) signals by using digitallyprogrammable switches, the passive sensitivities of which are very low. Equal capacitanceand equal resistance designs lead to vanishing the difficulty for accurately tuning the capacitances and resistances in integrated circuit (IC) fabrication.4. Focus on the design theory and method of current-mode high order filters isresearchedA lot of current-mode high order filters are researched with feedback method andanalytical synthesis method based on transfer function (ASM):(1) A current-mode filter with multiple inputs and multiple outputs based on MOCCIIsis presented. Various kinds of filters can be realized just by changing the amount andmode of joining external current signals to the circuit. Internal structure of circuit andamount of elements need not change. The circuit is convenient to be integrated.(2) It is presented a novel current-mode universal nth filter with equal capacitance andequal resistance and a new general synthesis method for arbitrary nth-order current- modeelliptic filter based on MOCCII. The universal nth filter circuit can complete all fivedifferent generic filtering at the output term by using digitally programmable switches, thesensitivities of which have a null sum partly and fully. It is also a good method to solvethe difficulty of synthesis method because of the complicated transfer function of thenth-Order Elliptic Filter and easy method to design the value of circuit elements.(3) A method of the nth order current mode leapfrog-type filter based on MCCCII ispresented. By defining the transfer function H_j(s)(I_o(j)/I_in) from the filter input to the outputof integrator j, the corresponding transfer H(s) of the all-pole filters and filters witharbitrary transmission zeros can be derived. Parameter values of the designed filter can beobtained from the coefficient matching equations based on the comparison between thenumerator and denominator polynomials coefficients of H(s)and the given H_d(S). Parametervalues of the designed filter can be computed easily.