New voltage-model/current-mode universal biquad filter using unity-gain cells

A new universal biquad filter is presented which can realize all the five standard filter functions namely lowpass, bandpass, highpass, notch and allpass in voltage-mode (VM) as well as in current-mode (CM) employing only unity-gain cells (i.e. voltage followers and current followers) as active elements. Explicit VM/CM outputs are available from low output impedance terminals and high output impedance terminals, respectively. The workability of the proposed universal biquad, realized with CMOS unity-gain cells, is established by SPICE simulations.     

Current-mode KHN-equivalent biquad using CDBAs

A new Kerwin-Huelsman-Newcomb (KHN)-equivalent biquad, operating in the current mode (CM), is proposed. The proposed circuit is derived from the adjoint graph of the signal flow graph corresponding to the classical KHN circuit. The derived circuit is a CM universal filter, which offers all the main advantages of CM circuits as well as those of the classical KHN circuit. The proposed circuit employs three current differencing buffered amplifiers (CDBAs) as active elements. In addition to the three basic filter responses, it also allows the realisation of the notch and allpass responses without requiring any element matching conditions     

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-$mu$m standard CMOS chip are provided.      

Electronically tunable versatile voltage-mode universal filter

A novel electronically tunable versatile voltage-mode universal biquad filter by using two single-output-operational transconductance amplifiers (OTAs), one differential difference current conveyor (DDCC) and two capacitors is proposed. The proposed circuit, which can be used as either a four-input single-output universal filter or a single-input three-output multifunction filter with the same topology. Besides, the new circuit offers the following advantageous features: realization of all the non-inverting and inverting biquadratic filter signals from the same configuration, no need to employ inverting-type input signals, no need to component-matching conditions and low passive sensitivity performance.     

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.     

Voltage mode universal filters employing single FDCCII

In this paper, four new voltage-mode universal biquad filters configuration are proposed. First of two circuits proposed high-input impedance universal filter with single-input and three-outputs, which can simultaneously realize voltage mode low-pass, band-pass and high-pass filter responses employing all grounded passive components. The third proposed universal filter three-input and single-output, which also can realize all the standard filter functions. The fourth circuit proposed universal filter with three-input and five-outputs, which can be used as either a three-inputs single-output or a two-inputs five-outputs universal filters. It can realize all five different generic filtering signals: low-pass, band-pass, high-pass, band-stop and all-pass. Simulation results are given to confirm the theoretical analysis. The proposed biquad filters are simulated using TSMC CMOS 0.35 μm technology.     

Novel universal current-mode filters using unity-gain cells

Two novel universal current-mode filters using unity-gain current followers (CFs) and voltage followers (VFs) are presented. The first one, employing three CFs, one VF, two grounded capacitors and two resistors, has two inputs and three outputs. The second one, employing only two CFs, one VF, two grounded capacitors and two resistors, has four inputs and a single output. Both proposed circuits oOEer the following advantageous features: universal current-mode filter realization from the same configuration, no requirements of component matching conditions, employment of two grounded capacitors ideal for integration, employment of two virtually grounded resistors good for voltage control, easy adjustment of ω₀/Q and ω₀ through separate virtually grounded resistors and low active and passive sensitivity performance.     

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.     

Single CCII-based voltage-mode universal filter

A new voltage-mode universal biquad filter is presented which can realize all the five standard filter functions namely lowpass, bandpass, highpass, notch, and allpass employing only one CCII as active element. The new circuit is composed of only one CCII, two capacitors, and three resistors, and realizes five generic filter signals without any inverting-type voltage input signals. This is unlike biquad reported by filter structures which employs more active components and needed an inverting-type voltage input signal to realize allpass signal.     

New universal biquad filters using only two unity-gain cells

New current-mode and voltage-mode universal biquad filters are presented using only two unity-gain cells (one current follower and one voltage follower) in each configuration. The proposed filters employ one less follower than in the literature to date. The filters can realize highpass, bandpass, lowpass, notch and allpass responses without any changes in the circuit topology. The circuits enjoy the following advantages: minimum number of active elements, no component-matching condition and low active and passive sensitivities.     

Cyclostationarity-based model for noise analysis of charge amplification with correlated double sampling

A lossless floating inductance has been simulated using two differential voltage current conveyors, two resistors and one grounded capacitor. The proposed floating inductance needs not component matching condition. Base on the proposed floating inductance as building block, a new voltage-mode universal biquadratic filter with one input and five outputs can be obtained. The proposed universal biquad uses two differential voltage current conveyors, three resistors and two grounded capacitors. All standard filter functions; highpass, bandpass, lowpass, notch and allpass can be obtained, simultaneously, without changing the passive elements. The proposed universal biquad has the features of using only grounded capacitors and orthogonal controllable of resonance angular frequency and quality factor.     

A new electronically tunable current mode universal filter using MO-CCCII

A new electronically tunable universal current mode biquad filter structure employing three multiple output current controlled conveyors (MOCCCII) and two grounded capacitors is presented. The proposed filter offers the following advantageous features: low input impedance and high output impedance—a desirable property of current mode filters; realization of low pass, band pass, high pass, notch, and all pass; no matching constraint; low sensitivity performance and use of grounded capacitors suitable for integration. The practical design problems due to nonlinearities of MOCCCIIs have also been addressed. The feasibility of the design is confirmed via SPICE simulations.     

Versatile universal voltage-mode filter employing DDCCs

A new versatile universal voltage-mode biquad with three inputs and five outputs using only two differential difference current conveyors (DDCCs), two grounded capacitors, and three resistors is proposed. The proposed configuration which can be used as either a single-input five-output filter or three-input two-output filter and which can simultaneously realize all five different generic filtering lowpass, bandpass, highpass, bandstop, and allpass signals is unlike the previously reported works and still enjoys (i) the employment all grounded capacitors, (ii) no need to employ inverting-type input signals, (iii) orthogonal control of the resonance angular frequency and the quality factor, (iv) simultaneous realization of lowpass, bandpass, highpass, bandstop, and allpass responses for the single-input five-output filter, and (v) no need to impose component choice to realize all five generic responses for the three-input two-output filter.     

Multi-function biquad using single current differencing transconductance amplifier

An universal multi input single output type multifunction biquad is proposed. The proposed configuration employs only one current differencing transconductance amplifier as the active element, two capacitors and three resistors. The circuit realizes all five filter functions (i.e. Low Pass, High Pass, Band Pass, Notch and All Pass) without changing the circuit topology. The natural frequency ω₀ is independently and electronically tunable. The workability of the proposed multifunction biquad has been verified using SPICE simulation.     

A 22.5 MHz current-mode KHN-biquad using differential voltage current conveyor and grounded passive elements

In this paper, a current-mode (CM) Kerwin–Huelsman–Newcomb (KHN) biquad is proposed. The circuit employs three differential-voltage current conveyors (DVCCs) as active elements together with two capacitors and four resistors as passive elements, which all are grounded. The circuit simultaneously provides the three basic filter functions, namely bandpass (BP), highpass (HP) and lowpass (LP) functions. The notch and allpass (AP) functions can be obtained by connecting appropriate output currents directly without using additional active elements. The output signals are obtained at high output impedance ports, which is important for easy cascading in CM operation. SPICE simulation results are given to verify the theoretical analyses.     

Realization of Voltage and Current Mode KHN Biquads Using CCCIIs

In this work, new Kerwin-Huelsman-Newcomb (KHN) biquads employing current-controlled current conveyors (CCCIIs) in voltage-mode (VM) as well as in current-mode (CM) are presented. The parameters of the proposed circuits can be electronically controlled thanks to the tunability properties of the CCCIIs. The VM circuit is derived from a previously reported one by modifying its summing circuit and replacing the current conveyor(CCIIs) and resistors at their x-input terminals with CCCIIs. On the other hand, the CM circuit is derived from the adjoint graph of the signal-flow graph corresponding to the classical KHN circuit. This circuit is a multi-input single-output CM universal filter, which offers all the main advantages of the CM circuits as well as those of the classical KHN circuit. In addition to the three basic filter responses, they also allow the realization of the notch and the all pass responses.     

Cascadable Current-Mode Biquad Filter and Quadrature Oscillator Using DO-CCCIIs and OTA

This article introduces a circuit which can function both as a quadrature oscillator and as a universal biquad filter (lowpass, highpass, bandpass). When the circuit functions as a universal biquad filter, the quality factor and pole frequency can be tuned orthogonally via the input bias currents. When it functions as a quadrature oscillator, the oscillation condition and oscillation frequency can be adjusted independently by the input bias currents. The proposed circuit can work as either a quadrature oscillator or a biquad filter without changing the circuit topology. The amplitude of the proposed oscillator can be independently controlled via the input bias currents. The proposed oscillator can be applied to provide amplitude modulated/amplitude shift keyed signals with the above-mentioned major advantages. The circuit is very simple, consisting of four dual-output second generation current controlled current conveyors (DO-CCCIIs), one operational transconductance amplifier (OTA), and two grounded capacitors. Without any external resistors and using only grounded elements, this circuit is therefore suitable for IC architecture. PSPICE simulation results are depicted here, and the given results agree well with the theoretical analysis. The power consumption is approximately 7.32 mW at ±2.5 V supply voltages.     

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.     

Second-order OTA-C filters derived from Nawrocki-Klein biquad

Based on the Nawrocki and Klein biquad and using different input and output techniques, many new filter structures and functions are developed from both voltage- and current-mode viewpoints. For example, it is found that the basic five operational transconductance amplifier (OTA) structure has the LP, BP, HP, BS and AP functions without the use of capacitor injection and component matching, a feature shared by no other existing two integrator loop OTA-capacitor (OTA-C) circuit, including the original NK biquad. Various BS, LPN, HPN, AP and universal architectures are obtained, which require fewer OTAs and may be more useful than the original biquad. This research shows that the NK biquad is one of the most important second-order OTA-C filters at least from the viewpoint of filter architectures and functions, and thus should receive attention in continuous-time filter design