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Electronically Tunable Current-Mode / Mixed-mode / Voltage-mode Multifunction Active-Only Biquads
N. A. Shah and M. F. Rather

A new electronically tunable active only multifunction filtering configuration with single input multi- output is presented. The filter constructed around three plus-type dual-output second generation current controlled conveyors (DO-CCCIIs) and two operational amplifiers (OAs) is fully integrable, programmable and suitable for high frequency operation. With current as input, the configuration simultaneously operates in current- mode (CM) and trans-impedance-mode (TIM) and realizes simultaneously lowpass (LP), bandpass (BP) and highpass (HP) in CM and TIM. In CM Notch (BR) and allpass (AP) signals are obtained by connecting the appropriate node currents, besides suiting cascadibility due to high output impedances while in TIM two of the three basic filtering functions offer low output impedances. When voltage acts as input, the configuration works simultaneously in voltage-mode (VM) and trans-admittancemode (TAM) and implements simultaneously LP, BP and HP in VM while in TAM only LP and BP responses are realized. VM topology offers high input- impedance and two of the three filtering signals are available at low output-impedances while in TAM input as well as the outputs are at high impedances. In addition to low sensitivity figures, the configuration in all the four modes show orthogonal electronic adjustment of natural frequency w0 and quality factor Q. The current and voltage tracking errors of the active devices have been included and SPICE simulation results are included, confirming the workability of the proposed circuit.

Keywords: Active-only, Current/mixed/voltage-mode filter, current controlled conveyors.

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