Log-domain Filters Research Articles

CMOS design of computational current-mode static and dynamic functions based on analog translinear cell

In this paper, the systematic realizations of some low-power nonlinear current-mode computational/configurable analog blocks (CABs) are presented. These CABs are based on a most demanded novel precise analysis and removal method of complete non-idealities of CMOS transistors. The proposed CAB architecture consists of a novel MOS translinear cell (MTC) that includes two overlapping up-down loops using MOS translinear principle (MTLP) in sub-threshold region. The proposed design with properly signal/bias injection scheme to MTC via NMOS-PMOS arrays is able to produce some current-mode nonlinear static and dynamic functions. Those are as vector summation, cube/third power, true RMS to DC converter and first-order low-pass log-domain filter. The designed functions are simulated by HSPICE simulator in TSMC 0.18 µm (level-49 parameters) CMOS technology. Pre and post-layout simulation results both plus Monte Carlo analysis are compared with other artworks that verified the functionality, flexibility and superiority of the proposed CABs.

The Design of Fifth-Order Butterworth Lowpass Log-Domain Filter for Bluetooth/Wi-Fi Receiver Using Signal Flow Graph Method

In this study, a fifth-order lowpass log-domain Butterworth filter, which is appropriate for Bluetooth/Wi-Fi receiver, is designed with signal flow graph approach. The filter is realized by using a unique translinear integrator circuit. Bluetooth and Wi-Fi modes are obtained without changing the circuit configuration. To change the mode of the filter, it is needed to change the cutoff frequency of the filter that can be electronically tuned by adjusting the external currents. Wi-Fi and Bluetooth receivers have 6[Formula: see text]MHz and 600[Formula: see text]kHz cutoff frequencies, respectively. Only BJTs and grounded capacitors were utilized to achieve the desired circuit. Lowpass log-domain Butterworth filter was simulated by using SPICE simulation program. A validated BJT and idealized BJT models are used to obtain simulation results confirming the theoretical analysis.

A new neuron and synapse model suitable for low power VLSI implementation

A new dynamical neuron model for low power and compact VLSI implementation is presented. The model is capable of generating the most common type of spiking patterns. Judicious use of subthreshold CMOS design techniques leads to a very effective low-power CMOS Neuron and synapse circuits. The circuit consists of a single first-order log domain filter and a few hyperbolic function generators. We have also developed a circuit which realizes the synaptic interconnections of the neurons. Based on this complete neuron and synapse model, we studied synchronization behavior of two reciprocally interconnected neurons with excitatory and inhibitory couplings. Owing to the use of log-domain design and current-mode design, the circuits occupying low chip area and having very low power consumption are obtained even at real biological time-scale operation. These features make these circuits especially suitable for hybrid interface applications and large scale VLSI neuromorphic networks.

Design of the adaptive log-domain low-pass filter

This paper presents the structure and realization method of the current-controlled adaptive low-pass filter which based on the design of LC ladder network. After amplifying, amplitude limiting and shaping, the input voltage signal was converted into frequency signal. Then by the broadband frequency-current conversion circuit it was converted into current signal which has a linear relationship with input frequency. The current signal was as the bias current to adjust the cut-off frequency of the log-domain low-pass filter. So that frequency of the filter can automatically track the input signal frequency. In this paper, the design principle was introduced in detail, the design formulas were derived and the circuit of adaptive second order log-domain low-pass filter was given. The filter can realize the scope of the cut-off frequency up to 30MHz. The tracking range for the input frequency is from 1MHz to 30MHz. The simulation results show the effectiveness of design method.

0.5 V Cardiac Sense Amplifier Realization Using Log-Domain Filtering

A novel configuration of a cardiac sense amplifier for pacemakers, realized using the concept of Log-Domain filtering, is introduced in this paper. The analog part of the amplifier operates under a single 0.5 V power supply voltage. Compared to the corresponding already published configuration, the proposed scheme offers the benefits of reduced operating voltage and dc power dissipation. The performance of the intermediate stages, as well as of the whole system, has been evaluated through the utilization of the Analog Design Environment of the Cadence software and, also, the design kit provided by the AMS 0.35 μm CMOS process.

Bursting Hodgkin–Huxley model-based ultra-low-power neuromimetic silicon neuron

This paper presents a compact, ultra-low-power implementation of the bursting Hodgkin---Huxley model-based silicon neuron. The Hodgkin---Huxley model is a neuron imitation that consists of two calcium current channels, a potassium current channel and a leakage current channel. In the proposed architecture, the calcium and the potassium current channels have been implemented using a sigmoid-function structure, a log-domain filter, and a linear transconductor. Different neuronal signals can be generated by changing the value of the capacitor in the log-domain filter. The proposed silicon neuron is capable of generating four different outputs, namely, spiking, spiking with latency, bursting, and chaotic signals. Ultra-low-power consumption is achieved by current-reuse technique and subthreshold region operation of MOSFETs. The circuit is designed using 0.13 μm standard CMOS process. The entire design uses 43 transistors, with a total power consumption of only 43 nW.

Novel log-domain frequency-adaptive filter

A topology for realising log-domain frequency-adaptive filters is proposed in this article. According to this the side effects of the on-chip capacitor deviations, generated by the technology tolerances, are efficiently compensated giving a constant cutoff frequency. Also, the cutoff frequency is automatically controlled and readjusted by the frequency of an external reference signal. The correct operation of the proposed scheme has been verified through simulations by employing transistor models provided by a typical 0.35 µm BiCMOS technology.

A Translinear, Log-Domain FPAA on Standard CMOS Technology

A field-programmable analog array (FPAA) using a standard-CMOS wide-dynamic-range translinear element (TE) is introduced. The FPAA configurable analog blocks (CABs) are based on a reconfigurable translinear cell (RTC), capable of implementing the basic circuit elements required by translinear and log-domain circuit design. The interfacing is provided by an I/O programmable cell, which allows for easier connectivity between the signal-processing core and the external circuitry. As a proof-of-concept, a 5 × 5 RTC FPAA testchip was implemented in 0.35- μm CMOS technology. A set of various circuit primitives, such as one- and four-quadrant multipliers, an Euclidean distance operator and a fourth-order log-domain filter, were mapped on the chip in order to demonstrate the versatility of the approach. FPAA bandwidth reaches 20 MHz with a power consumption of 30 μW/TE and precision errors below 3%.

A Generic Current Mode Design for Multifunction Grounded Capacitor Filters Employing Log-Domain Technique

A generic design (GD) for realizing annth order log-domain multifunction filter (MFF), which can yield four possible stable filter configurations, each offering simultaneously lowpass (LP), highpass (HP), and bandpass (BP) frequency responses, is presented. The features of these filters are very simple, consisting of merely a few exponential transconductor cells and capacitors; all grounded elements, capable of absorbing the shunt parasitic capacitances, responses are electronically tuneable, and suitable for monolithic integration. Furthermore, being designed using log-domain technique, it offers all its advantages. As an example, 5th-order MFFs are designed in each case and their performances are evaluated through simulation. Lastly, a comparative study of the MFFs is also carried, which helps in selecting better high-order MFF for a given application.

Log-domain all pass filter based on integrators

A new all-pass (AP) Log-domain filter is presented. The circuit is based on integrator loop and the current sources. The filter circuit has a very simple structure since it uses only bipolar junction transistors (BJT's) and a grounded capacitor. The configuration offers large dynamic range at low power supply and higher frequency operation. The filter has a large bandwidth due to its inherent current-mode (CM) nature and Log-domain properties. Phase angle can be electronically tuned through the bias current. The circuit can be implemented in integrated form. PSPICE simulations are given to confirm the theoretical analysis.

Log-Domain Filter Design Based on Impedance Scaling of LC Ladder Structures

In this paper, a log-domain filter design based on an impedance scaling technique of passive LC ladder structures is considered. To this end a general circuit for the simulation of any kind of two-terminal component, both grounded and floating, is presented. Depending on the kind of filter, the proposed technique can produce implementation advantages by reducing the number of required components. The validity of the approach is demonstrated through the simulation of a fifth-order LC ladder elliptic low-pass filter.

Wave log-domain filters using lattice sections

In this paper, the design of log-domain filters with uncommon transfer functions is considered, using the wave log-domain design method. To this end, the concept of log-domain wave equivalent of a lattice section is introduced, as a new building block, in order to enable the design of filters with transfer functions dealing with amplitude and phase response at the same time. This building block is very useful when the phase and the group delay response of the filter is significant. The functionality of this design approach is verified through a design example and simulation results. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of class-AB log-domain filters based on nonlinear transconductance

In this paper a new generalized method for synthesis of class-AB current-mode log-domain filters, using nonlinear transconductance cell, is presented. The proposed nonlinear transconductance cell is designed by employing floating-gate MOS (FG-MOS) transistors that operate in weak inversion. It allows deriving current-mode nonlinear transconductance-capacitor (Gm-C) structure from its corresponding conventional transconductance-capacitor (gm-C) in a systematic way. In this method, synthesis complexity is independent of system size, and thus high-order systems can be readily realized. In addition, it keeps the transconductance-capacitor topology invariant, leading to a very regular, general and simple topology. The filters are designed based on the transistors that are working in weak inversion and feature, low supply voltage, low-power consumption, immune to body effect and with low circuit complexity. For illustration of this new synthesis method, two different filters were designed and verified by simulation. The simulation results by HSPICE show the validity of the proposed technique.

Unifying perspective on log-domain filter synthesis

A unifying framework is presented for the in-depth understanding of the seemingly unrelated state-space-based and translinear methods proposed for the synthesis of externally linear but internally nonlinear log-domain filters. The translinear methods exploit either the ‘dynamic translinear principle’ or the Bernoulli Cell dynamics. Light is shed in an insightful manner on key interconnections between Frey's nodal state-space-based synthesis relations, translinear loop-based synthesis conditions and the archetypal linear filter dynamics by considering the form of the state variables used in each case.

Chemical log-domain filter

Presented is a chemical log-domain filter in which an ion sensitive field effect transistor (ISFET) is used to expand a naturally log-compressed chemical signal to derive a chemically-dependent lossy-integrator, whose gain and bandwidth are functions of ion concentration. This is used to integrate small chemical signals or have a filter adaptable to changes in chemical concentration.

A 19 nW analogue CMOS log-domain 6th-order Bessel filter without E-minus cells

This paper contributes to the field of low-power high-order CMOS log-domain filters by: (a) suggesting a log-domain synthesis path which bypasses the need for E-minus cells and (b) by assessing the practicality of the proposed synthesis path by means of a 6th-order CMOS log-domain Bessel filter fabricated in the commercially available AMS 0.35μm process. Measured results from the 19nW, 8–200Hz, 940μm2 Bessel filter chip confirm the validity of the proposed approach. The filter reported here is particularly useful for biomedical instruments such as portable ECG devices and Pulse-oximeters.

Log-domain synthesis of nth order universal filter

In this paper a synthesis approach for an nth-order universal log-domain filter comprising lowpass (LP), highpass (HP) and bandpass(BP) filtering functions is proposed. The approach is simple and the method of extending the approach to two uncommon filtering functions, lowpass notch (LPN) and high pass notch (HPN), is also given. The second, fourth and sixth-order universal log-domain filters are designed using log-exponential relationship between voltage and current of bipolar junction transistors (BJT) for the verification of approach. The performance of proposed universal filter and that of extended LPN and HPN was verified through simulation results.

Low-Voltage Log-Domain Complex Filters

Two systematic methods for designing low-voltage log-domain complex filters are introduced in this paper. The first one is based on the transposition of the signal flow graph representation of the linear-domain complex leapfrog prototype filter to the corresponding one in the log-domain. The last one is based on the transposition of the wave equivalents of the elements of the complex passive prototype filter to the corresponding log-domain complex equivalents. Both transpositions are performed by employing an appropriate set of complementary operators that facilitates the derivation of low-voltage log-domain filter configurations. Two design examples are given, where a 12th-order log-domain complex transfer function is realized in order to fulfill the Bluetooth specifications. The derived log-domain filter structures operate at a single 1.2-V-power supply-voltage, and their behavior was evaluated through simulation results. In addition, a comparison concerning important quality factors of both of the proposed structures is performed, and the obtained results are further discussed.

A LOG-DOMAIN WAVE POSITIVE IMPEDANCE INVERTER

A new log-domain building block for log-domain filter design is proposed in this paper. This block realizes a positive impedance inverter (gyrator) by using the log-domain wave method. A simple procedure for log-domain filter development, using the proposed block, is outlined. This method results in circuits, which are simple in structure and very easy to design. An example of a second-order bandpass filter is given and its functionality is verified through simulations.

DIFFERENTIAL LOG-DOMAIN WAVE ACTIVE FILTERS

In this paper, the design of differential log-domain wave filters is outlined which is based on the log-domain wave technique. The differential configuration is achieved by introducing the differential log-domain wave equivalent. The resulting filters inherit the good characteristics of the wave active filters, are very modular and easy to design. The method is demonstrated by a design example and its validity is verified through simulations results.