Current-mode Filter Research Articles

Design Considerations of Reconfigurable CMOS Mixers for Multi-Standard Communication Receiver Systems

This paper has been carried out the study of reconfigurable wide-band mixers that can do the frequency conversion and gain variation standards with low noise and high linearity used in multi-mode and multi-standard receivers. Over the last few years reconfigurability has become very popular in adopting technology to meet the wideband wireless communication specifications that is compatible with multi-standards like GPS (1.57 GHz), WLAN (2.4 GHz - 5.9 GHz), Bluetooth (2.402 – 2.483 GHz) and ZigBee (0.784 - 0.915 GHz) in low power consumption environment. The reconfigurability can be achieved between low and high band modes through power switching in RF frequency mixers. It can be achieved by flipping the input RF signal between gate and source terminal of input transistor and altering the trans-impedance stage output. With the concept of reconfigurable transistor pair with open and short circuit stubs, one can not only find the configurable gain with center frequencies 7.355, 8.65, 11.35 and 12.65 GHz but also with high power efficiency. Tow Thomas Bi-Quad Topology other than the traditional current commuting technique for the second order trans-impedance amplifier stage, works as a current mode filter over a tunable bandwidth. The active Gilbert mixers are used widely in most of communication system, due to its significance gain, perfect isolation, and linearity in response.

Design Considerations of Reconfigurable CMOS Mixers for Multi-Standard Communication Receiver Systems

This paper has been carried out the study of reconfigurable wide-band mixers that can do the frequency conversion and gain variation standards with low noise and high linearity used in multi-mode and multi-standard receivers. Over the last few years reconfigurability has become very popular in adopting technology to meet the wideband wireless communication specifications that is compatible with multi-standards like GPS (1.57 GHz), WLAN (2.4 GHz - 5.9 GHz), Bluetooth (2.402 – 2.483 GHz) and ZigBee (0.784 - 0.915 GHz) in low power consumption environment. The reconfigurability can be achieved between low and high band modes through power switching in RF frequency mixers. It can be achieved by flipping the input RF signal between gate and source terminal of input transistor and altering the trans-impedance stage output. With the concept of reconfigurable transistor pair with open and short circuit stubs, one can not only find the configurable gain with center frequencies 7.355, 8.65, 11.35 and 12.65 GHz but also with high power efficiency. Tow Thomas Bi-Quad Topology other than the traditional current commuting technique for the second order trans-impedance amplifier stage, works as a current mode filter over a tunable bandwidth. The active Gilbert mixers are used widely in most of communication system, due to its significance gain, perfect isolation, and linearity in response.

Current and Voltage Mode Resistorless Universal Biquad Filter Using a Single CCCDTA

Current mode (CM) Single-input and multi-output (SIMO) and Voltage mode (VM) Multi-input and single-output (MISO) biquad filters are proposed. The presented configurations use one Current controlled current differencing transconductance amplifier (CCCDTA) and two capacitors without any external resistors, which is easy suited for integrated circuit fabrication. The currentmode filter can realize the second-order low pass, band pass, high pass and band stop responses simultaneously. And the voltage-mode filter can realize all the standard filtering functions from the same structure. The natural frequency (ω) and quality factor (Q) of the filters can be controlled electronically by transconductance of the CCCDTA. Moreover, the proposed filters does not require any impedance matching due to its two input resistance can be independently tuned through the diverse external bias currents of CCCDTA. The influences of the CCCDTA non-idealities are also analyzed and both the active and passive sensitivities are considerably low. This design was simulated in PSPICE. Simulation results showed that their performances in power, bandwidth, out-band rejection and in-band ripple are better than the traditional. Additionally, the experiment results are provided in the paper.

Fully-differential current-mode higher order filters using all grounded passive elements

In this paper the realization of nth order (n ≥ 3) fully-differential current-mode filters using Current Differencing Current Conveyors (CDCC) has been presented which results in circuits employing all grounded passive elements. In contrast to earlier known realizations of fully-differential filters which invariably require more than one capacitors per pole, the proposed realization employs only one capacitor per pole. The cut-off frequency of the realized filter can be electronically tuned when all the grounded resistors associated with the integrators are implemented by identical CMOS grounded voltage-controlled-resistors (VCR) driven by a common control voltage. The methodology has been illustrated by realizing a fifth order Butterworth filter as a specific example whose workability has been verified using SPICE simulations in 0.18 µm TSMC technology. A reduced-component-version of the designed fifth order Butterworth filter has also been presented which also employs all grounded RC components but does not have electronic-tunability. Some representative simulation results have been included.

Electronically Tunable Current-Mode Third-Order Square-Root-Domain Filter Design

In this study, electronically-tunable, current-mode, square-root-domain, third-order low-pass filter is proposed. The study is carried out with three circuit designs. First circuit is third-order low-pass Butterworth filter, second circuit is third-order low-pass Chebyshev filter and the last circuit is third-order low-pass elliptic filter. All the input and output values of the filter circuit are current. Only grounded capacitors and MOSFETs are required in order to realize the filter circuit. Additionally, natural frequency [Formula: see text] of the current-mode filter can be adjusted electronically using outer current sources. To validate the theory and to demonstrate the performance of third-order filter, frequency and time domain simulations of PSPICE program are used. To that end, TSMC 0.35[Formula: see text][Formula: see text]m Level 3 CMOS process parameters are utilized to realize the simulations of the filter.

Tuning approach for first‐order filters and new current‐mode circuit example

An approach of tuning first-order filters is proposed in this study. The proposed approach is based on employing feedback in first-order filter circuits, wherein a scaled output is combined with the input signal, so as to facilitate easy tuning of filter parameters. Various options of tuning the filter parameters are explored by employing feedback from low-pass, high-pass or all-pass outputs. The approach enables easy tuning of filter parameters by varying the gain of an external amplifier, without adjusting the passive elements comprising the filter core. A new current-mode filter circuit is further proposed, which employs a recently introduced active element, namely an extra-X current conveyor. The new approach is used in the designed first-order filter circuit. The new proposed circuit benefits by employing only a grounded capacitor, exhibits low-input and high-output impedances. The approach of tuning filter parameters through external means, without disturbing filter core, and the new proposed circuit are verified through simulations with promising results. As further modification to the proposed approach, the possibility of realising pole–zero symmetry is presented, which makes the new proposed tuning method useful for both existing and future designs.

Nth order current mode universal filter using MOCCCIIs

This article presents a new current mode single-input-multiple-output nth order universal filter. The proposed circuit employs (n + 1) number multiple output second generation current conveyors and n number grounded capacitors only. Presented circuits can realize current mode low pass, high pass, band pass, notch and all pass responses simultaneously at different high output impedance terminals. The current mode filter circuit provides low input impedance by selecting the proper value of bias current and also has high output impedance, which is suitable for cascading. The circuit offers some important features such as resistor less realization, no passive component matching constraints, low sensitivity, electronic tunability and active-C realization. The functionality of the proposed filter circuit is tested with the PSPICE simulation, which is found to agree well with the proposed theory.

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 0.25µm TSMC CMOS technology parameters.

Programmable Universal Filters Using Current Conveyor Transconductance Amplifiers

This paper presents new programmable universal biquadratic filters using current conveyor transconductance amplifiers (CCTAs) by which both voltage- and current-mode filters can be obtained. The proposed filters use second-generation current conveyor (CCII) which is the first stage of CCTA to operate as current conveyor analog switch (CCAS) and this CCAS will be used to program the filtering functions such as low-pass, high-pass, band-pass, band-stop and all-pass filters. Unlike previous universal filters, the filtering functions of the proposed filters can be programmed using the bias currents of CCTAs without changing any input and output connections. The natural frequency and quality factor of all filtering functions can be controlled electronically and orthogonally using the bias currents of transconductance amplifiers. Also gain response of all transfer functions can be adjusted. The active and passive sensitivities of the filters are low. The proposed programmable filters have been simulated using 0.18[Formula: see text][Formula: see text]m CMOS process from TSMC. PSPICE simulation results are included to confirm workability of the proposed circuits.

CCCIIs-Based First-Order All-Pass Filter and Quadrature Oscillators

This paper introduces a current-mode first-order all-pass filter (APF) and its application in quadrature oscillator (QO) based on CCCII. The proposed filter can provide inverting and noninverting all-pass functions with a same circuit topology, it uses two CCCIIs and one grounded capacitor. Moreover, the first-order all-pass filter was applied in current-mode sinusoidal quadrature oscillators with the design based on block diagrams. The introduced oscillators can provide four phase-quadrature signals which independently control the condition of oscillation (CO) and frequency of oscillation (FO). The proposed oscillators consist of three CCCIIs and two grounded capacitors. The proposed APF and QOs have high output impedance which can directly drive load without additional current buffer. In addition, they use only grounded capacitors which are very appropriate to future development into an integrated circuit. The results of PSPICE simulation program correspond to the theoretical analysis.

Fully‐balanced four‐terminal floating nullor for ultra‐low voltage analogue filter design

This study presents a new complementary metal–oxide–semiconductor (CMOS) structure for a fully balanced four-terminal floating nullor (FBFTFN) which is suitable for ultra-low-voltage and low-power applications. This structure employs a bulk-driven quasi-floating-gate (BD-QFG) metal–oxide–semiconductor transistor technique to provide the capability of ultra-low-voltage, low-power operations as well as extended input voltage range. The functionality of the proposed circuits is demonstrated through simulations using SPICE and TSMC 0.18 µm n-well CMOS technology with supply voltage of 0.5 V and dissipation power of 9.4 µW. To confirm the attractive features of the proposed circuit, the fully balanced filters such as band-pass Sallen–Key filter, voltage-mode universal biquadratic filter and current-mode sixth-order low-pass filter using proposed BD-QFG FBFTFN as active elements have been designed.

Single CFTA Based Current-Mode Universal Biquad Filter

This paper introduces a new current-mode (CM) universal biquad filter structure with optimum number of active and passive elements. In the design, the proposed circuit uses a single active element namely, current follower trans-conductance amplifier (CFTA) and two grounded capacitors as passive elements. The main feature of the proposed circuit is that it can realize all five standard filtering functions such as low pass (LP), band pass (BP), high pass (HP), band stop (BS) and all pass (AP) responses across an explicit high impedance output terminal through the appropriate selection of three inputs. In addition, the same circuit is also capable to simultaneously realize three filtering functions (LP, BP and HP) by the use of single current input signal. Moreover, the proposed structure is suited for low voltage, low power operations and offers the feature of electronic tunability of pole-frequency and quality factor. Further to extend the utility of the proposed circuit block higher order current-mode filters are also realized through direct cascading. A detailed non-ideal and parasitic study is also included. The performance of the circuits has been examined using standard 0.25 μ m CMOS parameters from TSMC.

Resistor-Less Single-Purpose or Reconfigurable Biquads Utilizing Single z-Copy Controlled-Gain Voltage Differencing Current Conveyor

Presented work deals with applications of the single [Formula: see text]-copy controlled-gain voltage differencing current conveyor (ZC-CG-VDCC) in single purpose and multifunctional biquadratic voltage- and current-mode active resistor-less filters. Electronically adjustable features of the active device (intrinsic current input resistance [Formula: see text], current gain [Formula: see text] and transconductance [Formula: see text]) are controlled by DC bias current. These mentioned adjustable features allow interesting possibilities of control of the pole frequency and quality factor. Four voltage-mode solutions realizing low-pass, band-pass, high-pass and band-reject filtering solutions were designed together with two current-mode filters. The current-mode solutions have curious multifunctional capability based on full utilization of electronically controllable parameters of the ZC-CG-VDCC. Two adjustable parameters of the ZC-CG-VDCC (intrinsic current input resistance and transconductance) are used for electronic setting of features of the filter (pole frequency, quality factor, tuning). Control of the third adjustable parameter (current gain) causes reconnection-less change of the transfer function between iAP (inverting all-pass response) and iBR (inverting band-reject responses). Simulation results in PSPICE and Cadence CDS 6 are used to show characteristics of the proposed circuits.

Dual-parameter control of the pole frequency in case of universal filter with MCDU elements

This paper presents an universal filter with control of the pole frequency by two mutually independent parameters--current gain (B) and intrinsic resistance (Rx) in frame of two modified current differencing unit (MCDU) active elements. This type of control extends and also improves features of the tuning range and is referred to as dual-parameter control. The current-mode filter is of the second order and the required type of the response (low pass, inverting band pass, high pass, band reject and all pass) is obtained by proper selection/combination of input(s)--this filter is of the multiple-input single-output type. The filter employs two capacitors, two MCDUs, each of them with four controllable parameters and one multiple-output current follower. The paper includes tuning range analysis, the simulation results with behavioral models and also laboratory measurement results with the same models. Moreover, designed transistor-level structures of both the active elements proposed in ON Semiconductor I3T CMOS 0.35 um technology that were used for final simulations confirm the workability and features of the designed concept.

A Tunable Leapfrog Complex Filter for High Frequency and Wide Bandwidth Using Multi-Output Current Differencing Transconductance Amplifiers

ABSTRACTIn this paper, a new fourth-order complex (polyphase) filter is realized with the leapfrog structure. The proposed filter is based on the first-order stage using multi-output current differencing transconductance amplifiers (MOCDTAs). The design procedures for the realization of the first-order stage and fourth-order leapfrog polyphase filter are presented. In the procedures, the signal flow diagrams are also presented. The proposed design using MOCDTA simplifies the circuit of the current-mode leapfrog complex filter, where there are no resistors and with minimum number of active components. Besides, its centre frequency and bandwidth could be electrically tunable independently. The centre frequency of the proposed filter could be adjusted from 20 to 80 MHz, and its bandwidth could be more than 20 MHz. With ± 1.25 V supply, two examples of the proposed filter are introduced. Their bandwidths are from 46.1 to 68.5 MHz and from 22.3 to 48.4 MHz, respectively. Their image rejection ratios could be more than 59 and 39 dB, respectively. Meanwhile, both the IIP3s are over 18 dBm. The theoretical results are demonstrated by using SPECTRE simulation in CHRT 0.18 μm standard complementary metal oxide semiconductor (CMOS) process.

Multifunctional current-mode filter with dual-parameter control of the pole frequency

This paper presents a multifunctional current-mode filter with dual-parameter control of the pole frequency. The filter is of the second order, of single-input triple-output (SITO) typ ...

A 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS Current-Mode All-Pass Filter for Multi-GHz Operation

A CMOS wide-bandwidth first-order current-mode all-pass filter (APF) is discussed. The circuit consists of one transistor, a resistor, a grounded inductor, and a load. When used with a current mirror as the load, the current-mode filter exhibits a high output impedance, which is advantageous from an integration point of view and enables this configuration to be cascaded with current-mode circuits. The operation of the proposed circuit is experimentally validated. The APF implemented in IBM $0.13-\mu {\textrm {m}}$ CMOS was measured to have the pole-zero pair located at 8.32 GHz and to achieve a 55 ps group delay while consuming 19 mW from a 1.5-V supply. This paper experimentally demonstrates a CMOS APF that operates at multi-GHz frequencies and achieves the highest delay-bandwidth products of the published CMOS first-order APFs known to the authors.

Resistorless Reconfigurable nth-Order Filter Based on DPCDTA for Multi-mode Filtering Applications

This paper presents a new topology for realizing current-mode reconfigurable nth-order filter for multi-mode wireless communication equipments, which is based on a new active device, namely digitally programmable current differencing transconductance amplifier (DPCDTA). The proposed filter is resistorless, and it employs n DPCDTAs and n grounded capacitors with one input and one output terminals. The signal path of the filter does not contain any switches, and wide tuning coefficient of the filter is implemented using programmable current division network with zero standby power consumption in the DPCDTA. Also, the proposed topology exhibits broader programmable features to accommodate wide range of selectivity requirements, which can be used as the most compatible structure for field-programmable analog array and very suitable for multi-mode filtering applications. The programming ability of variable filter orders from first to fourth providing low-pass, high-pass, and band-pass responses, and programming ability of variable cutoff frequencies from 1.14 to 11.75 MHz are given as application examples. The performance of the circuits have been verified and evaluated through post-layout simulations using Cadence IC5141 with GlobalFoundries’0.18 μm CMOS process.

Realization of a New Current Mode Second-Order Biquad Using Two Current Follower Transconductance Amplifiers (CFTAs)

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.

Current Mode Universal Filter Using Single Current Controlled Differential Difference Current Conveyor Transconductance Amplifier

This research paper contains a new electronically tunable current-mode biquadratic universal filter using a new active building block; current controlled differential difference current conveyor transconductance amplifier (CCDDCCTA). The proposed filter provides the following important and desirable features: (i) One can use only one CCDDCCTA and two capacitors; (ii) One can get low pass (LP), band pass (BP), high pass (HP), notch (NF) and all pass (AP) current responses from the same configuration without any alteration; (iii) Passive components are grounded, which ease the integrated circuit implementation; (iv) Responses are electronically tunable; and (v) Sensitivity is low. Moreover, the non-ideality analysis shows that the parasitic passive components can be compensated for the proposed circuit. The functionality of the design is verified through SPICE simulations using 0.25 μm CMOS TSMC technology process parameters. Simulation result agrees well with the theoretical analysis.