Current-mode high-order OTA-C filters

A new way to implement current-mode continuous-time filters is presented which uses operational transconductance amplifiers (OTAs). Based on the simulation of a signal flow graph on the all-pole lowpass transfer function, the two current-mode realizations of high-order OTA-C filters are obtained.     

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     

基于MOCC的电流模式连续时间滤波器

本文利用多端输出电流传送器MOCC实现电流模式低通滤波器和通用滤波器。所提出的电路结构简单 ,所有无源元件均接地 ,便于CMOS工艺实现。     

Current mode continuous time wave active filters

Continuous time wave active filters using current mode processing are presented. The circuits derived are well suited for implementation as high frequency integrated filters. It is demonstrated that the important tuning process is simpler, and that current mode wave active filters are inherently adaptable.<>     

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.     

Differential current-mode tunable wave active filters based on single-ended wave port terminators

A method for the design of differential current-mode wave active filters, which is based on the use of single-ended wave port terminators, is presented in this paper. The resulting filters are modular and very simple to design while their cutoff frequency is controlled by a dc current, giving them the ability of frequency tuning. As an example a wide-band bandpass filter is realized by cascading a low-pass and a highpass filter. The overall filter has been integrated using a standard 0.35-/spl mu/m CMOS technology.     

Current-mode continuous-time filters using complementary current mirror pairs

A design of current-mode continuous-time filters for low voltage and high frequency applications using complementary bipolar current mirror pairs is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integration. Since the filters are based on the integrator type of realization, the proposed method can be used for a wide range of applications. The frequency of the filters can easily be changed by the DC controlling current. A fifth-order Butterworth and a third-order leapfrog filter with tunable cutoff frequencies from 20 MHz to 100 MHz are designed as examples and simulated by SPICE using standard bipolar parameters.     

Analysis and compensation of transistor non-idealities in log-domain wave active filters

A very important issue concerning the implementation of log-domain filters in integrated form is the effect of BJT transistor non-idealities. This paper is dealing with the above practical problem in the design of log-domain wave filters. For this purpose, a detailed analysis of the effects of the non-idealities on the frequency behavior of log-domain wave active filters is performed. In addition, a systematic method for compensating the caused imperfections is introduced. The validity of the proposed compensation scheme has been verified through simulation results.     

Current-mode lowpass and bandpass filters using the operational amplifier pole

This paper proposes a circuit configuration for realizing current-mode lowpass and bandpass filters using the operational amplifier (op.-amp.) pole. The circuit simultaneously realizes lowpass and bandpass transfer functions using an op.-amp., three resistors and a capacitor. The effects of the paras tic poles (i.e. second and third poles) of the op.-amp. on the gain of a lowpass filter are also presented. Since the circuit uses the op.-amp. pole, it is suitable for high frequency operation.     

Current-mode analogue interface for high-speed low-current differential signalling

In this work, we propose high-speed low-current differential signalling (LCDS) over an electrical chip-to-chip interconnect by using a common-gate transimpedance amplifier followed by a common-source TIA stage. LCDS uses a current-mode receiver compared to a conventional voltage-mode receiver used in most of the signalling technologies such as low-voltage differential signalling, voltage-mode signalling and current-mode logic. The minimum detectable signal level possible with a current-mode receiver for the targeted bit-error rate (BER) makes LCDS an attractive choice. Also the input impedance of the LCDS receiver can be made equal to 100 Ω differential for matching the characteristic impedance of electrical chip-to-chip interconnect. The complete design, analysis and noise characterisation of the TIA front-end is presented. The CGCSTIA is implemented in 1.8 V, 0.18 μm digital CMOS technology. The input-referred noise current and 3-dB bandwidth of the receiver are 1.57 μA and 5.75 GHz, respectively. For the targeted BER of 10^?12, a data transfer rate of 6 Gb/s is achieved, while transmitting the data over a FR4 PCB trace of length 20 cm. The power dissipated in the current-mode receiver is 3.6 mW.     

Log-domain wave filters

A systematic method for designing log-domain wave filters is presented. Wave filters simulate topologically and functionally passive doubly terminated LC ladder prototype filters of low sensitivity. The design in the log-domain is based on a transposition of the signal flow graph (SFG) that corresponds to the wave equivalent of elementary two-port blocks in the linear domain, to the corresponding log-domain SFG. This is achieved by using an appropriate set of complementary operators, in order to preserve the linear operation of the whole circuit. Simulation results of a fifth-order low-pass and a fourth-order bandpass log-domain wave filter are given, using HSPICE. The proposed circuits are suitable for low-voltage operation and in high-frequency applications.     

Current-mode square wave generators based on a single CDTA

This paper proposes two designs for current-mode square wave generators based on a current-differencing transconductance amplifier (CDTA). Both the proposed circuits are compact and employ a single CDTA with only two external passive components. The first circuit has a fixed duty-cycle topology and can generate a symmetrical square wave with variable frequency. The second circuit has a variable duty-cycle design and can operate in a current-controlled dual duty-cycle mode with a single-circuit topology. The proposed generators allow independent control of the operating frequency, output amplitude, and duty cycle by tuning diverse circuit parameters. This paper discusses several previous designs for square wave generators and presents the circuit principles, related governing formulas, and nonideal problems for the proposed circuits. In addition, computer simulations and experimental results, which are consistent with those of the theoretical analyses and confirm the feasibility of the new generators, are presented.     

Time-multiplexed active filters

The inductorless realization of high-order voltage transfer functions is achieved by subdividing a conventional realization into identical memoryless active subnetworks; the realization is then achieved by time multiplexing one of the memoryless active subnetworks such that it effectively replaces the total number of active subnetworks. The result of this time-multiplexing operation is to create a new type of RC-active filter that exhibits many practical advantages, such as lower power dissipation and a considerable saving in circuit complexity. The synthesis technique is illustrated by means of the design of a sixteenth-order low-pass transfer function. Nonideal performance is analyzed.     

Synthesizing active filters

The primary purpose of this article is to present a unified, comprehensive survey of accomplishments in the field of network synthesis for linear, lumped, and finite networks from 1965 through early 1968.* Because of the large number of contributions made during this period, only a sampling of the many significant works is presented here, with much of the material in the form of results. It is the author's hope that the extensive list of references included will be useful in providing the additional information necessary.     

Wave active filters

A method is described and implemented for the derivation of active RC filters from analogue passive filters of the lossless ladder doubly terminated kind. The method is based on scattering-parameter formulation and the active RC filters thus derived are referred to as wave active filters.     

Numerical integration of partial differential equations using principles of multidimensional wave digital filters

Physical systems described by partial differential equations (PDEs) are usually passive (due to conservation of energy) and furthermore massively parallel and only locally interconnected (due to the principle of action at proximity, as opposed to action at a distance). An approach is developed for numerically integrating such PDEs by means of algorithms that offer massive parallelism and require only local interconnections. These algorithms are based on the principles of multidimensional wave digital filtering and amount to directly simulating the actual physical system by means of a discrete passive dynamical system. They inherit all the good properties known to hold for wave digital filters, in particular the full range of robustness properties typical for these filters.In this paper, only the linear case is considered, with particular emphasis on systems of PDEs of hyperbolic type. The main features are explained by means of an example.     

Current-mode electronically tunable biquadratic filters consisting of only CCCIIs and grounded capacitors

In this paper, a current-mode (CM) analog filter for simultaneously realizing high output impedance low-pass, band-pass and high-pass analog responses besides high output impedance notch and all-pass analog filter responses with interconnection of the relevant output currents, is presented. Also, two CM filters for simultaneously providing high output impedance universal filter responses are derived from the proposed one. All of the introduced CM topologies employ a canonical number of only grounded capacitors without requiring any resistors, and do not need critical component matching conditions. All of the developed circuits have low input impedance and high output impedance resulting in easy cascadability with other CM ones. Frequency dependent non-ideal gain and parasitic impedance effects on the performance of the presented first filter are investigated as examples. In order the show the performance of the filter and verify the theory, simulations are accomplished with SPICE program.     

Brief communication Current-mode highpass and bandpass filters using the operational amplifier pole

A circuit configuration for realizing current-mode highpass and bandpass filters using the operational amplifier (op.-amp.) pole is proposed. The circuit simultaneously realizes highpass and bandpass transfer functions using an op.-amp., two resistors and a capacitor. The effects of parastic poles (i.e. second and third poles) of the op.-amp. are also presented. Since the circuit uses an op.-amp. pole, it is suitable for high frequency operation.     

Current-mode highpass, bandpass and lowpass filters using the operational amplifier pole

The use of the Operational Amplifier (OA) pole has received much attention for its potential advantages of miniaturization, ease of design and high frequency performance. This paper proposes a novel circuit configuration for realizing current-mode filters using the OA pole. The circuit realizes simultaneously highpass, bandpass and lowpass transfer functions. Since the circuit uses the OA pole, it is suitable for high frequency operation.     

Acoustic surface wave filters

Acoustic surface waves offer several advantages in the construction of delay lines and filters in the UHF range. In these devices the frequency response is determined by the finger spacing and overlap of the interdigital comb structures used as input and output transducers. Models are developed to describe these devices, and the predictions of these theories are compared with several experimental filters, including band-pass filters and dispersive delay lines.