Current-mode Universal Biquad Research Articles

Electronically tunable CFTA based positive and negative grounded capacitance multipliers

This paper presents four novel lossless grounded capacitance multiplier (GCM) circuits based on Current Follower Transconductance Amplifier (CFTA). Two of the proposed GCMs are positive and two are negative. The proposed GCMs include two CFTAs, two resistors, and a capacitor. The proposed GCMs employ a minimum number of passive components and do not require any passive element matching condition. The multiplication factor can be controlled either by bias current or by varying either of the two resistances. The effects of parasitic elements on the operating frequency range of the proposed GCMs have been investigated through mathematical analysis. Time and frequency domain analysis has been performed with LTspice program using 0.13 µm IBM CMOS technology parameters. The capacitance cancellation circuit and current-mode universal biquad filter applications are provided to demonstrate the usefulness of the circuit. Monte Carlo and temperature analyses have been performed to verify the robustness of the proposed GCMs. Additionally, comparison of the proposed GCMs with the relevant circuits previously reported in the literature is presented. An experimental example is provided to verify the time-domain performance of the proposed positive lossless GCM by using commercially available integrated circuits (ICs).

SINH-DOMAIN UNIVERSAL BIQUAD FILTERS

A family of current-mode universal biquad filters, realized using the concept of Sinh-Domain signal processing, is introduced in this paper. Both of them have the capability for operating in a low-voltage environment and, also, for orthogonal electronic adjustment between the resonance frequency and Q factor. Employing MOS transistors models from the AMS 0.35 μm process, the performance of the proposed topologies has been evaluated by exploiting the analog design environment of Cadence software.

CDTAs Based Current-Mode Universal Biquad Filters with Orthogonal Control of Quality Factor and Pole Frequency

This article presents current-mode universal biquad filters based on CDTAs. The filter circuits using four CDTAs and two grounded capacitors which are able to provide low-pass, high-pass, band-pass, band-reject and all-pass functions. The pole frequency can be orthogonally controlled from quality factor and the circuits have high output impedance appropriate for cascade connection application in current mode which is capable to directly drive load. This qualification is very appropriate for further development into an integrated circuit. The results of PSPICE simulation program are corresponding to the theoretical analysis.

An Active-Only Temperature-Insensitive Current-Mode Biquad Filter Based on Differentiator Structures Employing CCCCTAs

This article presents an active-only current-mode universal biquad filter performing three standard functions: low-pass, high-pass and band-pass function, which can be readily modified to achieve the rest functions (band-stop and all-pass). The circuit principle is based on active-only circuit designed by using differentiators which are constructed from current controlled current conveyor transconductance amplifier (CCCCTA) cooperating with an internally frequency compensated operational amplifier (OA). The features of the circuit are that: the pole frequency and quality factor can be independently tuned via the input bias currents and it is ideally temperature-insensitive, its circuit description is very simple, consisting of 3 CCCCTAs and 2 operational amplifiers, and the proposed circuit is very appropriate for further developing into integrated circuit architecture. The PSpice simulation results are shown. The given results agree well with the theoretical anticipation.

Universal Current-Mode Biquad Employing Dual Output Current Conveyors and MO-CCCA with Grounded Passive Elements

A new universal multiple input multiple output (MIMO) type current-mode biquad employing two dual output current conveyors (DOCCII), one multiple output current controlled current amplifier (MOCCCA) and four passive grounded elements is proposed which can realize all the five basic filtering functions namely, low-pass (LP), high-pass (HP), band-pass (BP), band-stop (BR) and all-pass (AP) in current mode from the same configuration. The centre frequency can be set by the passive elements of the circuit and the quality factor Q0 is electronically tunable through bias currents of the MOCCCA. Therefore, the biquad filter has independent tenability for the and Q0. The active and passive sensitivities of Q0 and are low. The workability of the new configuration has been demonstrated by PSPICE simulation results based upon a CMOS CCII in0.35μm technology.

A State Variable Method for the Realization of Universal Current-Mode Biquads

A state variable method of converting single-resistance-controlled- oscillators (SRCO), into universal current-mode biquad (offering realizations of all the five standard filter functions namely, low pass, band pass, high pass, notch and all pass) has been highlighted. The workability of the exemplary implementation of the derived current-mode universal biquad has been demonstrated by PSPICE simulation results based upon 0.35 μ m technology. It is expected that the proposed method can be applied to other SRCOs to generate other multifunction filter structures.

Universal biquad filters using low-voltage current mirrors

Novel Single Input Multiple Output (SIMO) and Multiple Input Single Output (MISO) current-mode universal biquad topologies are introduced in this paper. The proposed topologies have been realized by employing low-voltage current mirrors as active elements. As a result, an absence of resistors is achieved in the derived filter topologies; also only grounded capacitors are required. The resonant frequency of the filters can be electronically controlled by an appropriate dc current. In addition, the derived filters offer the feature of orthogonal adjustment between the resonant frequency and Q factor. The behavior evaluation of the proposed filters has been performed through a test chip prototype fabricated in AMS 0.35 μm CMOS technology.

Current-controlled current differencing transconductance amplifier and applications in continuous-time signal processing circuits

This article presents the design for a basic current-mode building block for analogue signal processing, named as Current Controlled Current Differencing Transconductance Amplifier (CCCDTA). Its parasitic resistances at two current input ports can be controlled by an input bias current. As it can be applied in current-mode of all terminals, it is very suitable to use in a current-mode signal processing, which is continually more popular than a voltage one. The proposed element is realized in a bipolar technology and its performance is examined through PSPICE simulations. They display usability of the new active element, where the maximum bandwidth is 65 MHz. The CCCDTA performs low-power consumption and tuning over a wide current range. In addition, some examples as a current-mode universal biquad filter, a current-mode multiplier/divider and floating inductance simulator are included. They occupy only single CCCDTA.

A CMOS Digitally Programmable Universal Current-Mode Filter

A new digitally programmable universal current-mode biquad filter is proposed. The filter is based on digitally controlled current followers (DCCFs). It utilizes gains of the DCCFs to provide precise frequency and/or gain characteristics that can be digitally tuned over a wide range. All parameters of the proposed filter can be adjusted independently. Experimental results obtained from a 0.35-mum standard CMOS chip are provided.

Universal current-mode biquad filter using dual output current differencing transconductance amplifier

A new universal current-mode biquad filter using current differencing transconductance amplifier (CDTA) is proposed. The proposed configuration can realize the second-order low pass, high pass, band pass, and band reject responses simultaneously. The circuit employs both grounded capacitors (ideal for integrated circuit implementation), and offers low active and passive sensitivities. The workability of the proposed configuration has been verified using SPICE simulation.

Current controlled current conveyor transconductance amplifier (CCCCTA): a building block for analog signal processing

This article presents a basic current-mode building block for analog signal processing, namely current controlled current conveyor transconductance amplifier (CCCCTA). Its parasitic resistance at current input port can be controlled by an input bias current. It is very suitable for use in current-mode signal processing, which is becoming more popular than voltage mode. The proposed element is realized in a bipolar technology and the performances are examined through PSPICE simulations, displaying usabilities of the new active element. The CCCCTA performs tuning over a wide current range. The description includes some examples as a current-mode universal biquad filter, voltage-mode universal biquad filter, a grounded inductance simulator, a current-mode multiplier/divider and an oscillator. They occupy only a single CCCCTA.

CMOS current-controlled current differencing transconductance amplifier and applications to analog signal processing

This article presents design of a basic current-mode building block for analog signal processing, named as current-controlled current differencing transconductance amplifier (CCCDTA). Its parasitic resistances at two current input ports can be controlled by an input bias current. Owing to working in current-mode of all terminals, it is very suitable to use in a current-mode signal processing, which is continually more popular than a voltage one. The proposed element is realized in a CMOS technology and is examined the performance through PSPICE simulations. They display usability of the new active element, where the maximum bandwidth is 311 MHz. The CMOS CCCDTA performs low power consumption and tuning over a wide current range. In addition, some examples as a current-mode universal biquad filter, floating inductance simulator and quadrature oscillator are included. They occupy only single CCCDTA.

On the Realization of Universal Current Mode Biquads Using a Single CFOA

The four terminal Current feedback op-amps (CFOA) with an external compensation pin, such as AD844, have received prominent attention during the past decade as alternative building blocks for analog circuit design because of their significant advantages over the traditional voltage-mode op-amp (VOA). A popular application of CFOAs has been in realizing voltage-mode (VM) and current-mode (CM) biquad filters. Previously known universal CM biquads (i.e. those capable of realizing all the five generic filter functions namely, low-pass, band-pass, high-pass, notch and all-pass) realizable with CFOAs require two to nine CFOAs. Although a few dual-function/three-function single-CFOA-based CM circuits have appeared in literature, no single-CFOA-based canonic universal CM biquad with explicit CM output has been reported in the literature up until now. This paper fills this void by presenting a set of eight minimal universal CM biquads all of which are realizable with only a single CFOA. The non-ideal analysis of the proposed circuits has been presented, their comparative features, advantages and limitations have been brought out. The workability of all the proposed circuits has been confirmed by PSPICE simulations and experimental results based upon AD844 type CFOAs.

Universal current mode biquad using a single CFOA

Because of their several advantages over the traditional voltage mode op-amp, current feedback op-amps (CFOAs) have attracted prominent attention as alternative building blocks for biquad filter realization. Previously known universal current mode (CM) biquads (i.e. those capable of realizing all five generic filter functions, namely low-pass, band-pass, high-pass, notch and all-pass) are realizable with CFOAs but require two to nine CFOAs. Although a few dual-function/three-function single-CFOA-based CM circuits have appeared in the literature, no single-CFOA-based canonic universal CM biquad with explicit CM output has been reported until now. This paper presents such a circuit. The workability of the proposed circuit has been confirmed by PSPICE simulations based upon AD844-type CFOAs.

Novel electronically controllable current-mode universal biquad filter

A novel electronically-controllable universal current-mode biquad realisable with only three multiple-output second generation Current-Controlled Conveyors (CCCII), two grounded capacitors and one grounded resistor (which can also be implemented electronically) is presented which offers a number of advantageous features, not available simultaneously in any of the previously known electronically-controllable single-input-multiple-output type CM universal CCCII-based biquads. The proposed circuit is eminently suitable for implementation in both bipolar and CMOS/BiCMOS technologies. The workability of the new biquad configuration has been demonstrated by SPICE simulation results.

Novel versatile insensitive universal current-mode biquad employing twosecond-generation current conveyors

A new universal current-mode biquad with two inputs and three outputs or threeinputs and two outputs using only two second-generation current conveyors andfour grounded/virtual-grounded passive elements is proposed. The proposed circuithas the following advantages: simultaneous realization of five generic current-modefilter signals from the same configuration; no requirements of any cancellationconstraints; employment of two grounded capacitors ideal for integrated circuitimplementation; employment of two grounded/virtually grounded resistorssuitable for voltage control; orthogonal adjustment of ω0/Q and ω0 through twoseparate grounded/virtually-grounded resistors; high output impedance good forcascadability for the current-mode circuits; and low active and passive sensitivities.

Current-mode universal filter using unity gaincells

A new universal current-mode biquad filter circuit suitable for integrated circuit implementation is presented. The circuit uses three two-output current followers, two voltage buffers, two grounded capacitors and four virtually grounded resistors to realise all the standard biquad filters without changing the circuit topology. The proposed circuit can be used to achieve independent control of the natural frequency and the bandwidth. Also, the filter exhibits a low input impedance, high output impedance as well as low active and passive sensitivities. Simulation results using CMOS unity gain cells are also presented.

Current-mode and voltage-mode universal biquads using a single current-feedback amplifier

A new current-mode universal biquad and a new voltage-mode universal biquad using a single current-feedback amplifier are proposed in this paper. Both biquads enjoy the following advantages: realization of highpass, bandpass and lowpass filtering from each configuration, avoidance of input voltage tracking error in a current-feedback amplilfier; only one active component; no requirement for match components; low passive and active sensitivities. An inverting amplifier is used to form a notch filter. Experimental results are obtained to prove the theoretical analyses.

Integrated universal biquad based on triple-output OTAs and using digitally programmable zeros

The authors describe how triple-output OTAs facilitate the development of a new current-mode universal biquad configuration capable of generating various filter transfer functions using digitally programmable zeros. This is achieved without excessive use of active devices and without changing the biquad topology. The biquad zeros may be independently programmed using four switches producing the following filtering functions: LP, HP, BP, BR, AP, and lowpass notch. Further advantages of the biquad are (W0 and Q) electroinc tunability, low sensitivity and ease of design. Fabricated in a 0.8µm double-metal, double-poly CMOS process, the universal biquad occupies an active chip area of 0.6 mm 2 . For demonstration purposes, simulated and measured results of voltage tunable lowpass and bandpass filters over the frequency range of 0.7MHz to 8MHz are included.

Parasitic-capacitance-insensitive current-mode filters using operational transresistance amplifiers

A parasitic-capacitance-insensitive MOSFET-C integrator and differentiator using operational transresistance amplifiers are proposed and experimental results demonstrated. The bandwidths of these circuits are also independent of their gains. The required capacitances are smaller than those in previous work. Two new configurations of universal current-mode biquad filters based on these circuits are presented. A second-order bandpass filter constructed using universal biquad filters and another third-order Chebyshev lowpass filter with 0.1 dB passband ripple are breadboarded and the measured results presented.