Reconfigurable Voltage-Mode First-Order Multifunction Filter Employing Second-Generation Voltage Conveyor (VCII) With Complete Standard Functions and Electronically Controllable Modification

In this contribution, the realization of a first-order, two-input, single-output voltage-mode multifunction filter employing a second-generation voltage conveyor (VCII) is described. The proposed first-order versatile filter is extremely simple, composed of a single VCII and three passive devices. Because of its low output impedance, the output voltage node can be easily cascaded with other voltage-mode configurations without the requirement of any buffers. In the same circuit topology, the proposed firstorder filter provides various filtering functions: inverting and non-inverting low-pass (LPF), inverting and non-inverting high-pass (HPF), as well as inverting and non-inverting all-pass (APF). The digital method allows the selection of output first-order filtering functions without the need for additional circuits such as inverting or double-gain amplifiers. Furthermore, the pass-band gain of the low-pass and high-pass responses can be adjusted by varying the resistance or capacitance values without influencing the pole frequency as well as the phase response. The influence of VCII's current/voltage gain errors and parasitic elements on filtering performance is also investigated. Moreover, the modification of the proposed lagging phase allpass filter to achieve electronic controllability is also proposed by replacing the passive resistor with the operational transconductance amplifier (OTA). The 0.18 mu mTSMCCMOSstructure of the VCII employed in the proposed filter operates in the subthreshold region and utilizes the bulk-driven technique (BD), enabling it to operate with 0.4V supply voltage and consuming 383 nW of power. The total harmonic distortion (THD) of the LPF with an applied input voltage V-inpp =300mV @ 50Hz is -49.5 dB. An application example as a quadrature sinusoidal oscillator realized from the proposed first-order allpass filter and lossless integrator is also included. The performance of the proposed reconfigurable voltage-mode first-order filter is simulated and experimentally tested using a commercially available AD844 IC-based VCII with +/- 5 V power supply.