Study On Fully Integrated Continuous-time OTA-C Active Filters

A continuous time filter is a front subject in microelectronics, circuits and systems. It applies widely in communication, electronic measurement, instrument & appearance and cybernation. Especially it has an important application in mixed signal circuits of digit and analog, communication IC. OTA-C active filters research is one extremely active subject in the modern filter domain. OTA-C active filters may become the most potential because they have good high frequency characteristic and electrically controlled ability, greatly strengthened circuit synthesis ability and compatibility with MOS VLSI technology.The dissertation studies the realization method of OTA and the structures, realizations and design methods of OTA-C second-order and high-order filters. At first each kind of integrated filter and respective characteristic and this topic vital significance and present international and domestic research states are introduced. Basic structure and model and principle of work of MOS transistor and several kinds of basic intrgrated circuit unit module are then introduced. Basic concept and application principle and the structure of OTA are then introduced. Furthermore a systematic design theory and method of filters based on MO-OTAs from matrix theory is proposed. A voltage mode three inputs and one output second-order multiple function filter is proposed. It can realize five basic biquadratic filtering characteristics of lowpass, highpass, bandpass, notch and allpass. A novel current mode OTA-C multifunction biquadratric filter is proposed. It can not only realize five basic biquadratic filtering characteristics of lowpass, highpass, bandpass, notch and allpass at a output terminate, but also realize multiple function filtering outputs at the three output terminates simultaneously. Two kind of filters above with minimum components is composed of three OTAs and two capacitors. At the last a new arbitrary order OTA-C multifunction filter is proposed which is composed of 2n+2 OTAs and n capacitors. Itcan realize lowpass, highpass, bandpass, bandstop and allpass filtering outputs. A current-mode n-order OTA-C highpass filer is proposed which is only composed of n OTAs and n capacitors. Above two kind of filters all the capacitors are grounded. The circuits is integrated conveniently and is compatible with VLSI technology.PSPICE simulation results of proposed filter circuits are given. A current-mode n-order OTA-C highpass filer is made. Experimental result is similar to the simulation result to confirm the theoretical analysis.