High input impedance voltage-mode universal biquadratic filter using two OTAs and one CCII

A three-input and single-output voltage-mode universal biquadratic filter with high input impedance, using only two operational transconductance amplifiers (OTAs), one plus-type second-generation current conveyor (CCII) and two capacitors, is presented. The proposed circuit can realize all the standard filter responses, that is, highpass, bandpass, lowpass, notch and allpass filters, from the same configuration. The proposed circuit has no requirements for component matching conditions.     

Voltage-mode FDCCII-based universal filters

Three new voltage-mode universal biquadratic filters configuration are proposed. The first proposed high-input impedance universal filter with single input and five outputs, which can simultaneously realize voltage-mode lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filter responses employing all grounded passive components. The second proposed high-input impedance universal filter with three input and single output, which also can realize all the standard filter functions without requiring any inverting input voltage signal. The third proposed universal filter with three inputs and five outputs, which can be used as either a three-input single-output or a two-input five-output universal filter. Moreover, each of the proposed circuits still enjoys (i) the employment of only grounded capacitors, and (ii) no requirement with the component choice conditions to realize specific filtering functions.     

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.     

Voltage-Mode New Universal Biquad Filter Configuration Using a Single VDIBA

A universal voltage-mode filter configuration employing a voltage differencing inverting buffered amplifier (VDIBA), two capacitors and a resistor is proposed. The presented structure can realize all the five standard biquadratic filters: low-pass, high-pass, band-pass, band-reject and all-pass, without changing the circuit topology. The proposed filter circuit also provides the following advantageous features, not available simultaneously in any of the single active element/device based universal biquad realizing all the five filter responses known earlier so far: (i) independent electronic tuning of natural angular frequency (ω ₀) and bandwidth (BW), (ii) no requirement of any element matching condition or inversion of input signal(s) (as needed in most of the earlier reported structures), and (iii) low active and passive sensitivities. Moreover, even the internal structure of the new building block is possibly the simplest among all recently introduced new building blocks. The workability of the proposed filter has been confirmed by SPICE simulations using 0.18 μm technology.     

Single-input four-output voltage-mode universal filter using single DDCCTA

An electronically tunable universal voltage-mode biquadratic filter with single input and four outputs using one differential difference current conveyor transconductance amplifier (DDCCTA), two resistors and two grounded capacitors is proposed. All the five standard biquadratic filter functions; lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP), can be obtained from the circuit configuration. The LP, BP and HP are simultaneously available without component matching condition. By imposing component choice, the BS and AP responses can also be realized from the same circuit configuration. In addition, the proposed circuit provides an electronic control of its natural angular frequency (ω₀) and quality factor (Q) by adjusting the bias current of the DDCCTA. The simulation results together with the ideal values are also given to demonstrate the performance of the proposed circuit.     

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.     

High output impedance current-mode universal biquadratic filters with five inputs using multi-output CCIIs

Three current-mode universal biquadratic filters each with five input terminals and one output terminal are presented. The first proposed circuit uses three multi-output second-generation current conveyors, two grounded capacitors and three resistors. This circuit offers the following advantageous features: orthogonal controllability of resonance angular frequency and quality factor, high output impedance, the versatility to synthesize all standard filter types without component matching condition and using grounded capacitors. The second proposed circuit uses three multi-output second-generation current conveyors, two grounded capacitors and two resistors. This circuit offers the following advantageous features: using minimum passive components, high output impedance, the versatility to synthesize all standard filter types without component matching condition and using grounded capacitors. The third proposed circuit uses three multi-output second-generation current conveyors, two grounded capacitors and three grounded resistors. This circuit offers the following advantageous features: the versatility to synthesize all standard filter types, high output impedance and using only grounded passive components. Each of the proposed circuits can get five kinds of filter functions by using only one current input signal.     

Negative Impedance Converter With Reduced Nonideal Gain and Parasitic Impedance Effects

In this paper, two novel negative impedance converter (NIC) structures are proposed. One of the introduced NICs exhibits the property of both simultaneously reduced nonideal gain and parasitic impedance effects. Also, the other one shows the property of reducing only parasitic impedance effects and employs only second-generation current conveyors; accordingly, it can be realized with commercially available active devices such as AD844s. In order to show the performance of the introduced NICs, a versatile circuit employing a minimum number of active and passive elements for all the analog filters and lossy inductor simulators is developed. The proposed topology with appropriate component and input port selections gives four kinds of lossy grounded simulated inductors as well. Further, the presented multipurpose circuit is the first one that provides both of the current-mode and voltage-mode standard universal filter responses as well as synthetic inductors from the same topology. The developed topology employing only grounded capacitors can also realize transimpedance-mode low-pass and bandpass responses simultaneously; thus, it is convenient for integrated circuit (IC) realization. Likewise, positive lossy inductor simulators consist of a grounded capacitor. Nevertheless, the realized circuit requires a single resistive component-matching condition. Simulation results using SPICE program and experimental results are included to verify the theoretical ones.      

New universal filter using only current followers as active elements

A new universal current-mode (CM) biquad filter is presented which can realise all the five standard filter functions namely lowpass, bandpass, highpass, notch and allpass employing only unity-gain current followers (CF) as active elements. The workability of the proposed universal biquad, realised with CMOS unity-gain current followers, is established by SPICE simulations. The new circuit provides explicit CM outputs from high output impedance terminals and possesses a number of advantageous features all of which are not available simultaneously in any of the previously reported CF-based universal biquad filters.     

Synthesis of a first-order passive complex filter with band-pass/band-elimination characteristics

In this paper, a new passive complex filter is proposed. In the same fashion as the traditional real band-pass filter, the proposed circuit is also designed through the frequency transformation. In order to obtain the prototype complex filter suitable for passive realization, the extended lowpass–highpass transformation or the bilinear lowpass–lowpass transformation different from the well-known frequency shifting method is adopted. These transformations give two filters; however, the final circuits become identical to each other. The proposed circuit has two output terminals. One is the complex band-pass output, and the other is for the complex band-elimination. The proposed circuit includes a capacitor, an autotransformer or an inductor and termination resistors only. Because the proposed circuit has terminating resistors at both of the input and the output sides, it is suitable for high frequency application. As an example, two first-order complex filters which operate in 100 kHz and 10 MHz are designed and their frequency responses are measured. It is shown that the measured frequency responses agree with the theoretical ones through experiment.     

Current mode filters with reduced complexity using a single EX-CCCII

In this paper an active element Extra-X current controlled conveyor (EX-CCCII) is used to reduce the complexity of some existing circuits. Two second-order current-mode biquadratic filter circuits are proposed, each using a single active element and two grounded capacitors. The first circuit is three input single output (TISO) and the second one is single input three outputs (SITO) biquadratic filter. The First circuit can realize all the standard filter transfer functions, while the second circuit can realize LP, BP and HP responses. The study of non-idealities and parasitics of the active element and their effects on transfer functions is carried out. The new circuits are found to be simpler than the earlier ones in terms of number of transistors. The functionality of the proposed biquadratic filters is verified through detailed PSPICE simulations using 0.25 µm TSMC CMOS technology parameters.     

New current-mode current-controlled universal filter with single input and three outputs

In this study, a new current-mode current-controlled universal filter with single input and three outputs is presented. The proposed circuit uses single-output current controlled conveyors (CCCIIs) and can simultaneously realize lowpass, bandpass and highpass filter functions all at high impedance outputs. Realization of notch and allpass responses does not require additional active elements. The circuit enjoys independent current-control of the parameters ω₀ and ω₀/Q without disturbing the gains of the lowpass, bandpass and highpass filters. Both its active and passive sensitivities are low.     

Integrable Current-Mode Filter Realisation using Dual-Output Current Conveyors for Low-Frequency Operation

The realisation criteria of continuous-time current-mode (CM) active filters for low frequency operation are investigated. New lossless and lossy integrators for low frequency operation using dual-output current conveyors (DO-CCII) are proposed. Basing on these building blocks, a CM universal filter with low natural frequencies suitable for integrated circuit implementation is presented. Using the proposed filter, natural frequencies as low as a few ten hertz can be achieved on an integrated circuit chip without using any external passive components. The proposed circuit simultaneously produces three basic filter responses at its high impedance outputs and it has good passive and active sensitivity performance.     

Electronically controlled high input and low output impedance voltage mode multifunction filter with grounded capacitors

In this study, a three-input single-output voltage-mode biquadratic filter employing voltage differencing differential input buffered amplifier (VD-DIBA) is presented. The proposed filter uses two VD-DIBAs and two grounded capacitors without any external resistors, which is well suited for integrated circuit implementation. The circuit provides five standard transfer functions, namely, low pass, high pass, band pass, notch and all pass filters with electronic control of quality factor and pole frequency. Each transfer function can be selected by suitably selecting input signals via digital method. The filter does not require inverting of the input voltage signal. Moreover, the circuit possesses high input and low output impedances and thus it enables simple voltage-mode cascading. The PSPICE simulation and also experimental results are included, verifying the workability of the proposed filter. The given results agree well with the theoretical anticipation.     

High Input Impedance Voltage-Mode Universal Biquadratic Filter with Three Inputs and Six Outputs Using Three DDCCs

A new high input impedance voltage-mode universal biquadratic filter with three input terminals and six output terminals is presented. The proposed circuit uses three plus-type differential difference current conveyors (DDCCs), three resistors, and two grounded capacitors. The proposed circuit can realize all the standard filter functions, namely, lowpass, bandpass, highpass, notch, and allpass, simultaneously, without component matching conditions. The proposed circuit still offers the features of high input impedance, using only grounded capacitors, and orthogonal controllability of resonance angular frequency and quality factor.     

Multiple-Mode OTA-C Universal Biquad Filters

Two new multiple-mode (including voltage, current, transconductance, and transresistance modes) OTA-C universal biquad filters are proposed. The first proposed circuit uses only four operational transconductance amplifiers (OTAs) and two grounded capacitors. The second proposed circuit uses five OTAs and two grounded capacitors. Both the proposed circuits can realize voltage, current, transconductance, and transresistance mode universal filtering responses (low-pass, high-pass, band-pass, notch, and all-pass) from the same topology. The first proposed circuit uses the least number of components. This represents an attractive feature from a chip area and power consumption point of view. The second proposed circuit has no need of extra inverting and non-inverting amplifiers for special input signals. Moreover, both the proposed biquads still have (i) the employment of two grounded capacitors, (ii) cascadable connection of the former voltage-mode stage and the latter current-mode stage, and (iii) low sensitivity performance. H-SPICE simulation results confirm the theoretical analysis.     

High input impedance voltage-mode universal biquadratic filters with three inputs using plus-type CCIIs

Two new configurations for realizing high input impedance voltage-mode universal biquadratic filters are presented. Each proposed universal biquadratic filter with three inputs is composed of three plus-type CCIIs and can realize all the standard filter functions, that is, highpass, bandpass, lowpass, notch and allpass filters. In spite of the active components, the first proposed configuration uses five passive components, the second proposed configuration uses three capacitors and three resistors. The use of only plus-type CCIIs simplifies the configurations.     

Current-mode universal filters using unity-gain cells

Two new current-mode universal filters are presented. The proposed filters use unity gain current and voltage followers. The first filter has three inputs and one output and can realise lowpass, highpass and bandpass responses without any changes in the circuit topology. Realisation of notch and allpass responses can be easily achieved without adding any additional active elements. The second filter has three inputs and one output and can simultaneously realise lowpass, highpass and bandpass responses without any changes in the circuit topology. Realisation of notch and allpass responses can be easily achieved without adding any additional active elements. The proposed circuits enjoy low active and passive sensitivities     

High Input Impedance Voltage-Mode Universal Biquadratic Filter with One Input and Five Outputs Using Current Conveyors

A new high input impedance voltage-mode universal biquadratic filter with one input terminal and five output terminals is presented. The proposed circuit uses three differential voltage current conveyors (DVCCs), four resistors, and two grounded capacitors. The proposed circuit can realize all the standard filter functions—lowpass, bandpass, highpass, notch, and allpass—simultaneously, without changing the passive elements. The proposed circuit enjoys the features of high input impedance, orthogonal control of resonance angular frequency and quality factor, use of only grounded capacitors, and low active and passive sensitivities.     

Universal filters of arbitrary order and type employing square-root-domain technique

Novel Single Input Multiple Output (SIMO) and Multiple Input Single Output (MISO) universal filter topologies of arbitrary order and type are introduced in this paper. The proposed topologies have been realised by employing Square-Root Domain (SRD) technique. An offered benefit of the universal filter topologies is that only grounded capacitors are required for their implementations and the resonant frequency of the filters can be electronically controlled by an appropriate dc current. The proposed universal filters simultaneously offer all the five standard filtering functions i.e. Lowpass (LP), Highpass (HP) and Bandpass (BP), Bandstop (BS) and Allpass (AP) frequency responses. In addition, the SIMO topology is generic in the sense that it can yield four different stable filter configurations. Two design examples are provided in each configuration and the correct operation of the corresponding topologies has been evaluated through the PSPICE software with BSIM 0.35-µm CMOS process model parameters.