Improved fully-balanced current-mode integrator

A high CMRR fully-balanced current-mode integrator structure is presented. The proposed structure improves the CMRR at low frequencies by a factor of g_m/g_o. Moreover, the structure provides more flexibility to guarantee stability and is significantly less sensitive to process mismatches. The differential and common-mode gains and CMRR at low and high frequencies are analysed as well as verified in simulation     

Design of low-voltage and low-power fully integrated filter based on log-domain current-mode integrator

In this paper a novel log-domain current-mode integrator based on MOS transistors in subthreshold is proposed. The integrator's time-constant is tunable by varying a reference bias current. By use of the integrator, a fifth-order Chebyshev lowpass filter with 0.1dB ripples is designed. The simulation results demonstrate that the proposed filter has such advantages as low power supply(1.5V), very low power dissipation (μW level), nearly ideal frequency response, very small sensitivity to components in passband, and adjustable cut-off frequency over a wide range. The circuit is composed of NMOS transistors and grounded capacitors which make it suitable for fully integrated circuit implementation.     

CMOS continuous-time current-mode filters for high-frequencyapplications

Design considerations for high-frequency CMOS continuous-time current-mode filters are presented. The basic building block is a differential current integrator with its gain constant set by a small-signal transconductance and a gate capacitance. A prototype fifth-order low-pass ladder filter implemented in a standard digital 2 μm n-well CMOS process achieved a -3 dB cutoff frequency (f ₀) of 42 MHz; f₀ was tunable from 24 to 42 MHZ by varying a reference bias current from 50 to 150 μA. Using a single 5 V power supply with a nominal reference current of 100 μA, the five-pole filter dissipated 25.5 mW. The active filter area was 0.056 mm²/pole. With the minimum input signal defined as the input-referred noise integrated over a 40 MHz bandwidth, and the maximum input signal defined at the 1% total intermodulation distortion (TIMD) level, the measured dynamic range was 69 dB. A third-order elliptic low-pass ladder filter was also integrated in the 2 μm n-well CMOS process to verify the implementation of finite transmission zeros     

Distributed current-mode image processing filters

Presented is a new design method for distributed focal plane image processing, which allows complementary metal oxide semiconductor (CMOS) implementation of two-dimensional, reconfigurable, image-processing kernels at the pixel level.     

基于跨导放大器的电流模式积分单元的设计

在集成电路系统中,各种模拟功能的电流单元都是由基本的电流模单元组成。跨导放大器是电流模电路的基本单元。基于跨导放大器的电流模积分器可以实现电流到电流的积分转换。同时可应用于各种集成滤波电路的设计。在此采用0．18ptmCMOS仿真工艺,使用共源共栅结构设计一款供电电压为1．8V的高增益低功耗的跨导放大器,采用具有PTAT基准电流源的偏置电路,使用HSpice进行优化设计,并将此放大器应用于电流模式积分单元的电路仿真。     

Fully differential bilinear integrator for SC filters

A fully differential bilinear SC integrator, which can be used for SC filter realisations, is proposed. It is parasitic-insensitive and particularly useful in SC filters simulating analogue ladder networks. The design of these filters is different from the commonly used ones, and leads to filters with better sensitivity properties than earlier versions. Realisation of a third-order highpass filter, bilinearly transformed from the continuous-time to the discrete-time domain, is shown as an example.     

Cascadable current-mode filters using single FTFN

This comment relates to a previously published letter (see M.T. Abuelma'atti, ibid., vol.32, pp.1457-8, 1996) which presents a cascadable universal current-mode second-order filter using a single four-terminal floating nullor (FTFN) with low active and passive sensitivities. In it, the authors suggest an amended expression for the current-transfer function     

基于MOCCII多功能电流模式滤波器

本文提出一种新型基于MOCCII多功能电流模式二阶滤波器电路,该滤波器电路仅由2个MOCCII及4个RC元件构成,无需元件匹配就能同时实现低通、带通、高通、带阻及全通滤波输出.该电路所有的RC元件均接地,且有很低的灵敏度.文中对滤波器的非理想特性进行了分析.最后对提出的电路进行了计算机仿真.     

Cascadable current-mode filters using single FTFN

A new configuration for realising current-mode filters using a single four-terminal floating nullor (FTFN) is presented. It can realise lowpass, bandpass, highpass, notch and allpass filters from the same configuration. This configuration has a high output impedance. So the synthesised current-mode filters can be cascaded without additional buffers. Moreover, the resultant current-mode filters will be insensitive to the current tracking error of an FTFN. Experimental results that confirm the theoretical analyses are obtained     

Widely tunable low-power high-linearity current-mode integrator built using DG-MOSFETs

A novel tunable current-mode integrator for low-voltage low-power applications is presented using mixed-mode TCAD simulations. The design is based on independently driven double-gate (IDDG) MOSFETs, a nano-scale four-terminal device, where one gate can be used to change the characteristics of the other. Using current-mirrors built with IDDG-MOSFETs, we show that the number of active devices in the tunable current-mode integrator, 16 in bulk CMOS design, may be halved, i.e. considerable savings in both total area and power dissipation. The integrator operates with single supply voltage of 1 V and a wide range of tunable bandwidth (~2 decades) and gain (~30 dB). This linear circuit has third-order harmonic distortion as low as ?70 dB in appropriate bias conditions, which can be set via the back-gates. The impact of tuning on the IDDG integrator and conventional design using symmetrically driven (SDDG) MOSFETs is comparatively studied. The proposed design is a good example for performance leverage through IDDG MOSFET architectures in analog circuits integral to future mixed-signal systems.     

Novel current-mode active-only biquad with loss-less and lossy integrators

This paper presents a realization of a current-mode active-only biquad with a two-integrator loop structure. The proposed circuit is constructed solely with operational amplifiers (OAs) and operational transconductance amplifiers (OTAs). The circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions, and the circuit characteristics can be electronically tuned by adjusting the transconductance gains of the OTAs. An example is given together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.     

Current-mode integrator for voltage-controllable low frequency continuous-time filters

A novel differential current-mode integrator (CMI) for voltage-controllable low frequency continuous-time filters is presented. An example fifth-order lowpass filter using the proposed CMI and on-chip capacitors was implemented in an AMI 1.2 /spl mu/m CMOS process, and it achieved -3 dB cutoff frequencies ranging from 160 Hz to 5.6 kHz, by changing a single control voltage.     

Cascadable current-mode filters using single FTFN

A new configuration for realising cascadable current-mode second-order filters using the single four-terminal floating nullor (FTFN) is presented. The proposed realisations have low active and passive sensitivities and use six passive elements at most     

Digitally programmable high-order current-mode universal filters

New high-order current-mode (CM) filter topologies capable of providing all functions simultaneously are presented. The proposed filters are based on digitally controlled current amplifiers and unity gain voltage buffers. The gains of the current amplifiers are digitally programmed to adjust the filters’ transfer function coefficients. It is shown that the proposed approach results in more efficient realizations compared with its counterparts based on other CM active elements. Using BSIM3 0.18 μm CMOS models, simulation results of a fourth-order universal filter are provided.     

Stability problems in universal current-mode filters

Analog circuit designers have usually focused on the design of circuits employing a minimum number of components, occupying less area and dissipating less power. However, some important issues such as signal limitations and especially stability problems of the analog circuits have not received considerable attention in the literature. Hence, the work described in this paper deals with the stability problems of two new current-mode analog filters employing multiple output current controlled conveyors (MOCCCIIs). Toward that end, a single pole model is replaced for each non-ideal current gain of the MOCCCIIs. Both of the novel universal current-mode active-C filters can simultaneously realize low-pass, band-pass and high-pass/notch filter responses. SPICE and MATLAB simulation results are given to verify the theoretical analysis.     

Structural design of current-mode biquad filters

This work describes how to generate and design a novel current-mode biquad filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-pass, band-pass, high-pass, notch and all-pass are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The simulation results are also presented to confirm the theoretical analysis.     

Economical RC active lossy ladder filters

The letter describes a class of RC active filters derived from RLC lossy ladder-filter prototypes. The presence of loss in the prototypes allows the use of active building blocks containing only one amplifier. Design methods are outlined, and ways of reducing sensitivity are discussed. The filters are economical in the number of amplifiers required, and a comparison indicates that they can be significantly less sensitive than active filters built as a cascade of non-interacting sections.     

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.     

High impedance voltage- and current-mode multifunction filters

This paper presents a voltage- and current-mode multifunction filters based on and employing two four-terminal floating nullors (FTFNs) and a single operation transconductance amplifier (OTA). The high-input impedance voltage-mode configuration can simultaneously realize lowpass (LP), bandpass (BP) and notch filtering functions from the same configuration. The circuit employs two grounded capacitors which suits contemporary IC design techniques. The resonance frequency ω₀ and bandwidth ω₀/Q can be independently tuned while as resonance frequency ω₀ and quality factor Q are orthogonally controllable. The current-mode configuration can simultaneously realize LP and highpass (HP) from which notch filtering signal can also be obtained. The input impedance of the circuit is very low while the output currents are available at very high impedances. The resonance frequency ω₀ and bandwidth ω₀/Q can be orthogonally tuned. The high impedance of both the topologies in the two modes facilitates easy cascading for higher-order filter construction. Passive sensitivity figures are low. PSPICE simulation results are also included.