An active-only electronically controllable current-mode multifunction filter using CCCFTAs

This paper presents a voltage-mode biquadratic filter performing completely standard functions: low-pass, high-pass, band-pass, band-reject and all-pass functions, based on single voltage differencing transconductance amplifier (VDTA). The proposed filter has three input voltage and a single output voltage. The features of the circuit are that; the quality factor and natural frequency can be tuned independently; the circuit description is very simple, consisting of merely one VDTA, one resistor and two capacitors; the pole frequency can be electronically adjusted. Additionally, each function response can be selected by suitably selecting input signals with digital method; the double input voltage is not required. Using only single active element, the proposed circuit is very suitable to further develop into an integrated circuit. The PSPICE simulation results are depicted. The given results agree well with the theoretical anticipation.

In this paper a new current-mode multifunction filter using opamp compensation poles is presented. The proposed circuit is composed of two internally compensated operational amplifiers (OAs) and five single output operational transconductance amplifiers (OTAs), without using external passive elements. The proposed multifunction filter can realize lowpass, bandpass, highpass and bandstop responses simultaneously all at high output impedances. The circuit is suitable for monolithic implementation either with CMOS or bipolar technologies. All of active sensitivities are low. The performances of the circuits are tested using SPICE simulation program.

In this paper, a new non-integer-order (fractional-order) low-pass filter with independent electronic control of the order, quality factor and pole frequency is presented. The filter operates in the current mode and uses Operational Transconductance Amplifiers (OTAs) and Adjustable Current Amplifiers (ACAs) as active elements. The values of non-integer order, quality factor and pole frequency of the filter are controlled by the internal and electronically controllable parameters of the used active elements (transconductance, current gain in our case). The proposed filter allows tunability of the pole frequency in range from 43.0 to 364.0 kHz. The filter order is controlled from 1.17 to 1.75 and finally it provides possibility to control quality factor from 0.64 to 1.9. Features of the proposed circuit are verified by PSpice simulations using transistor-level simulation models of the active elements.

This paper presents the second-order current-mode filter with 4 input currents and single output current. Five filter responses, namely High-pass (HP), Low-pass (LP), Band-pass (BP), Band-reject (BR) and All-pass (AP) filters are achieved. The pole frequency and quality factor are tuned by input bias current called electronic control. It has high output impedance which is able cascading in the current-mode filter and driving load without buffering devices. The filter uses only single active element namely current controlled current differencing transconductance amplifier (CCCDTA) and 2 grounded capacitors which is ideal for monolithic integrated circuit implementation. The filter was proved by Pspice simulation using BJT technology. The results are agreed with theoretical prediction.

A circuit which can function both as quadrature oscillator and as a universal biquad filter (low-pass, high-pass, band-pass, band-reject and all-pass functions) is introduced in this paper. Working as quadrature oscillator, the oscillation condition and oscillation frequency can be adjusted independently with the input bias currents. Functioning as a universal biquad filter, the quality factor and natural frequency can be tuned orthogonally via the input bias currents. The proposed circuit can work as either a quadrature oscillator or a universal biquad filter without changing circuit topology. The proposed circuit description is very simple, consisting of merely 2 current controlled current conveyor transconductance amplifiers (CCCCTAs) and 2 grounded capacitors. Without any external resistors and using only grounded elements, this circuit is thus suitable for IC architecture. The PSPICE simulation results are depicted, and the given results agree well with the theoretical anticipation. The maximum power consumption is approximately 3.78 mW at plusmn1.5 V power supplies.

MOS-C realizations of the Kerwin–Huelsman–Newcomb (KHN) circuit using the commercially available Voltage Operational Amplifier (VOA) and the Current Feedback Operational Amplifier (CFOA) are reviewed in this paper. Additional MOS-C KHN realizations using the Operational Transresistance Amplifier (OTRA) and the Differential Current Voltage Conveyor (DCVC) are also included. MOS-C realizations of the KHN circuit using CMOS operational amplifier, CMOS current feedback operational amplifier and CMOS operational transresistance amplifier are also given.Spice simulation results using 0.18 CMOS technology model from MOSIS are included together with detailed comparison tables to demonstrate the differences between MOS-C KHN circuits using both of the commercially available active building blocks and CMOS integrated building blocks. A comparison with the Gm-C KHN circuit is also included.

A three-input single-output multi-function filter based on voltage differencing gain amplifiers (VDGAs) as active devices is introduced. The proposed circuit consists of 3 VDGAs and 2 capacitors, without any resistor, suitable to implement into integrated circuit architecture. The proposed circuit can provide 5 standard filter functions including lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass filter (AP) without changing structure. The outstanding feature of the mentioned filter is that the natural angular frequency (ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ) and quality factor (Q) can be controlled independently through transconductances of the VDGAs. The total power consumption of proposed circuit is 0.82mW.

A new circuit for realization of universal current-mode filter using current Follower Transconductance Amplifiers (CFTAs) is presented. The proposed circuit realizes current-mode low pass, high pass and band pass filter functions simultaneously with a single current source at the input. The band reject and all pass filters can also be obtained from the proposed circuit without any extra hardware. The proposed circuit employs three passive grounded elements and two CFTAs. Linear electronic control of natural frequency ω0 is available in the proposed circuit. The quality factor can be independently adjusted through grounded resistor. The proposed circuit employs two grounded capacitors and a grounded resistor along with two CFTAs. The grounded resistor can be replaced by an OTA based circuit for linear electronic control of quality factor Q0. The circuit exhibits low active and passive sensitivities for ω0 and Q0. Simulation results are obtained using PSPICE software which is in conformity with the theoretical findings.

This paper presents design of electronically reconfigurable fractional-order filter that is able to be configured to operate as fractional-order low-pass filter (FLPF) or fractional-order high-pass filter (FHPF). Its slope of attenuation between pass band and stop band, i.e., order of the filter, is electronically adjustable in the range between 1 and 2. Also, pole frequency can be electronically controlled independently with respect to other tuned parameters. Moreover, particular type of approximation can be also controlled electronically. This feature set is available both for FLPF and FHPF-type of response. Presented structure of the filter is based on well-known follow-the-leader feedback (FLF) topology adjusted in our case for utilization with just simple active elements operational transconductance amplifiers (OTAs) and adjustable current amplifiers (ACAs), both providing possibility to control its key parameter electronically. This paper explains how reconfigurable third-order FLF topology is used in order to approximate both FLPF and FHPF in concerned frequency band of interest. Design is supported by PSpice simulations for three particular values of order of the filter (1.25, 1.5, 1.75), for several values of pole frequency and for two particular types of approximation forming the shape of both the magnitude and phase response. Moreover, theoretical presumptions are successfully confirmed by laboratory measurements with prepared prototype based on behavioral modeling.

Improved realization of canonical Chua's circuit with synthetic inductor using current feedback operational amplifiers

This article presents a current-mode quadrature oscillator using current controlled current feedback amplifiers (CC-CFAs) as active elements. The proposed circuit is realized from a lossy integrator and a lossy differentiator. The oscillation condition and oscillation frequency can be orthogonally controlled via input bias currents. The circuit description is very simple, consisting of merely 2 CC-CFAs, one grounded and floating capacitors. Without any external resistors and using a few number of external passive components, the proposed circuit is then suitable for IC architecture. The proposed circuit, due to high output impedances, enabling easy cascading in current-mode signal processing. The PSPICE simulation results are depicted, and the given results agree well with the theoretical anticipation. The power consumption is approximately 327µW at ±1.5V supply voltages.

Current mode multifunction filter using two CDBAs

A low power current controllable single-input three-output current-mode filter using MOS transistors only

This paper suggests a single-input multi-output (SIMO) multi-function current mode active filter design using three voltage differencing transconductance amplifiers (VDTAs) as an active element. The filter is realized in current-mode (CM) and delivers several filter operations such as HP, LP, BP, BR and AP filter functions with appropriate connections of input signal. The filter consists of three VDTAs and two capacitors, which are grounded. The significance of the suggested filter is that it provides electronic and independent controllability of filter parameters i.e. pole frequency (ωp) and Q-factor (Q). The filter design is analyzed using Virtuoso Analog Design Environment of Cadence.

Based on the fifth-order voltage-mode low-pass LC ladder structure the active only grounded-C equivalent circuit solutions are presented. As active building blocks the current follower transconductance amplifiers (CFTAs) are used. Using the signal flow graph approach, the initial solution using nine active elements is further optimized to a more simple topology employing only six active elements and five capacitors. Using the readily available UCC-N1B integrated circuit, the performance of the optimized active only grounded-C voltage-mode low-pass filter has been verified both by the simulations and the experimental measurements.