Positive Feedback Source Research Articles

On improving the performance of dynamic positive-feedback source-coupled logic (D-PFSCL) through inclusion of transmission gates

Dynamic positive feedback source-coupled logic (D-PFSCL) gates are used as a low power alternative in mixed signal applications over static positive feedback source coupled logic (PFSCL) gates. In this paper, transmission gates (TG) are included in the dynamic positive-feedback source coupled logic (D-PFSCL) architecture. The proposed scheme allows implementation of logic functions which in existing schemes is restricted to NOR/OR only or three input AND/OR only realization forms. The significant reduction in the number of stages, dynamic current sources and self-timed buffer with proposed scheme leads to efficient D-PFSCL design in comparison to the existing ones. Simulations using PTM 65 nm technology node at frequency of 1 GHz are performed. A maximum improvement of 40.8%, 73% and 97% in delay, dynamic power consumption and EDP respectively is been observed for D-PFSCL exclusive-OR(XOR2) gate implemented using proposed scheme with respect to existing D-PFSCL schemes. Further, a study on the trade-off between power dissipation and frequency of operation is included for the completeness.

Impact of multi threshold transistor in positive feedback source coupled logic (PFSCL) fundamental cell

Impact of multi threshold transistor in positive feedback source coupled logic (PFSCL) fundamental cell

Increased CO2 efflux due to long-term experimental summer warming and litter input in subarctic tundra – CO2 fluxes at snowmelt, in growing season, fall and winter

Soils of northern latitude tundra ecosystems have accumulated large amounts of carbon that might be released as CO2 when temperature rises and the tree-line moves north. We aim to investigate the potential CO2 flux changes at a subarctic tundra heath under changing climate. We measured daytime ecosystem respiration and photosynthesis at a subarctic heath over a full year under ambient conditions and in factorial long-term (13 years) increased summer temperature and leaf litter addition plots, and in additional short-term (2 years) summer warming plots. Under ambient conditions the ecosystem was a daytime sink of CO2 in the five warmest months, but a net daytime source in the cold season. Thirteen years of summer warming by 1 °C at soil surface increased CO2 emissions, as daytime respiration increased by 37% and photosynthesis by 29% over the year. Short-term warming likewise increased fluxes. Litter addition also increased the emission of CO2 as ecosystem respiration rose by 21% but photosynthesis remained unchanged. Both warming and litter addition significantly enhanced the amount of green biomass. This study suggests that in a changed climate subarctic ecosystems will act as a positive feedback source of atmospheric CO2. It shows the significance of CO2 fluxes outside the growing season and demonstrates a cold-season long- but not short-term legacy effect of increased summer warming on CO2 emission.

Mathematical Analysis of a Prototypical Autocatalytic Reaction Network.

Network autocatalysis, which is autocatalysis whereby a catalyst is not directly produced in a catalytic cycle, is likely to be more common in chemistry than direct autocatalysis is. Nevertheless, the kinetics of autocatalytic networks often does not exactly follow simple quadratic or cubic rate laws and largely depends on the structure of the network. In this article, we analyzed one of the simplest and most chemically plausible autocatalytic networks where a catalytic cycle is coupled to an ancillary reaction that produces the catalyst. We analytically analyzed deviations in the kinetics of this network from its exponential growth and numerically studied the competition between two networks for common substrates. Our results showed that when quasi-steady-state approximation is applicable for at least one of the components, the deviation from the exponential growth is small. Numerical simulations showed that competition between networks results in the mutual exclusion of autocatalysts; however, the presence of a substantial noncatalytic conversion of substrates will create broad regions where autocatalysts can coexist. Thus, we should avoid the accumulation of intermediates and the noncatalytic conversion of the substrate when designing experimental systems that need autocatalysis as a source of positive feedback or as a source of evolutionary pressure.

Adjustably transconductance enhanced bulk‐driven OTA with the CMOS technologies scaling

An adjustably transconductance enhanced bulk-driven operational transconductance amplifier (OTA) working at weak inversion region is presented. Based on the traditional positive feedback source degeneration technique, a proposed current-shunt auxiliary amplifier is employed here to modulate the gate of input differential pairs, achieving a further improvement of the effective transconductance with the CMOS technologies scaling. In addition, an adjustable transconductance enhancement factor is obtained, leading to an enhanced stability performance. Both conventional and proposed bulk-driven OTAs are designed and simulated on CSMC 180 nm process. The simulated results demonstrate that the unity gain-bandwidth of the proposed bulk-driven OTA is improved by 120% compared to that of the conventional counterpart with a little neglected increased power consumption.

A 63‐dB gain OTA operating in subthreshold with 20‐nW power consumption

SummaryThis paper presents a two‐stage bulk‐driven operational transconductance amplifier operating in weak‐inversion region. The proposed amplifier is upgraded using recycling structure, current shunt technique, positive feedback source degeneration and indirect frequency compensation feedback to enhance transconductance under a reasonable stability. Combining these approaches leads to an ultra‐low‐power high performance amplifier without increasing power dissipation compared to the conventional one. Simulation results in 0.13‐µm complementary metal–oxide–semiconductor technology show the proposed structure achieves a 63‐dB DC gain at 0.25‐V supply voltage with just 20‐nW power dissipation. Copyright © 2016 John Wiley & Sons, Ltd.

Bus Implementation Using New Low Power PFSCL Tristate Buffers

This paper proposes new positive feedback source coupled logic (PFSCL) tristate buffers suited to bus applications. The proposed buffers use switch to attain high impedance state and modify the load or the current source section. An interesting consequence of this is overall reduction in the power consumption. The proposed tristate buffers consume half the power compared to the available switch based counterpart. The issues with available PFSCL tristate buffers based bus implementation are identified and benefits of employing the proposed tristate buffer topologies are put forward. SPICE simulation results using TSMC 180 nm CMOS technology parameters are included to support the theoretical formulations. The performance of proposed tristate buffer topologies is examined on the basis of propagation delay, output enable time, and power consumption. It is found that one of the proposed tristate buffer topology outperforms the others in terms of all the performance parameters. An examination of behavior of available and the proposed PFSCL tristate buffer topologies under parameter variations and mismatch shows a maximum variation of 14%.

Starch: Application of biopolymer in random lasing

Here we report on the possible application of starch as a dye-doped biopolymeric matrix designed for random lasing generation. Gelatinized biopolymer doped with Rhodamine 6G was used as light amplification medium as well as source of positive feedback which is originating from high surface roughness fluctuations. It is demonstrated that, applying the starch as a matrix for laser dye we can significantly increase photostability of laser emission with respect to other biopolymeric based systems which is great advantage of this material.

A 60-dB Gain OTA Operating at 0.25-V Power Supply in 130-nm Digital CMOS Process

This paper presents a 60-dB gain bulk-driven Miller OTA operating at 0.25-V power supply in the 130-nm digital CMOS process. The amplifier operates in the weak-inversion region with input bulk-driven differential pair sporting positive feedback source degeneration for transconductance enhancement. In addition, the distributed layout configuration is used for all the transistors to mitigate the effect of halo implants for higher output impedance. Combining these two approaches, we experimentally demonstrate a high gain of over 60-dB with just 18-nW power consumption from 0.25-V power supply. The use of enhanced bulk-driven differential pair and distributed layout can help overcome some of the constraints imposed by nanometer CMOS process for high performance analog circuits in weak inversion region.

Design Methodology for Screening Dynamic Characteristics of Candidate Heat-Integrated Flowsheets

Well-established design methods exist for generating candidate heat-exchanger networks (HENs), but there is a strong need for a methodology to screen for undesirable dynamic characteristics that are often observed in heat-integrated processes. In this paper, a simple transfer function-based method is developed that can assist in comparing dynamic behavior of candidate heat-integrated flowsheets. Use of the method allows the design engineer to determine the dynamic characteristics of the overall process shortly after identifying exchanger networks that satisfy the process heat balance. Mathematical development of the method is given, followed by explanations of its use. The basis of the method is developed in block-diagram format, making apparent the source of positive feedback that can result from adding heat integration to a process. Finally, the method is demonstrated on three candidate HENs for a simple process. The method allows for identification of dynamic characteristics that would not be determine...

Oscillations and Mechanistic Analysis of the Chlorite−Sulfide Reaction in a Continuous-Flow Stirred Tank Reactor

Sustained oscillations in pH and redox potential are found in the chlorite-sulfide reaction in a continuous-flow stirred tank reactor (CSTR). Autocatalytic oxidation of HSO(3)(-) by ClO(2)(-) is the major source of positive feedback of hydrogen ions. The reaction between H(2)S and ClO(2)(-) to form S(8), which consumes H(+), is an important source of negative feedback. A model consisting of five protonation-deprotonation equilibria and nine redox reactions is proposed for the oscillatory reaction between S(2-) and ClO(2)(-). The 10 species included are HS(-), H(2)S, S(2)O(3)(2-), SO(3)(2-), HSO(3)(-), OCl(-), HOCl, ClO(2)(-), H(+), and OH(-). In contrast to the H(2)O(2)-S(2-) oscillatory reaction, S(2)O(3)(2-) is shown here by capillary electrophoresis to be an important intermediate. Simulations give qualitative agreement with the pH oscillatory behavior observed in the CSTR.

An Organic-Based pH Oscillator

In a recent paper, we suggested that the acid- or base-catalyzed dehydration of a hydrated carbonyl compound provides a suitable foundation for an organic-based pH oscillator. Here we present the first experimental example of such an oscillator in a flow reactor, utilizing the base-catalyzed dehydration of methylene glycol as a source of positive feedback (OH- autocatalysis) coupled with the base-catalyzed hydrolysis of gluconolactone for negative feedback (H+ production). The large amplitude oscillations (between pH 7 and 10) are reproduced in a kinetic model of the reaction. Such experiments present new possibilities in the design of pH oscillators.

Self-esteem maintenance processes: why low self-esteem may be resistant to change.

If most people desire to maximize feelings of self-worth, how do we explain the persistence of low self-esteem? Results from four studies suggest that people with low self-esteem may be less likely to accept positive feedback from themselves than from an outside source but equally likely to accept negative feedback from the self and an outsider. When the self was the source of positive feedback, people high, but not low, in self-esteem incorporated the feedback into their self-views; in contrast, when positive feedback came from a knowledgeable external source, both high and low self-esteem people accepted it. Finally, when self-generated feedback was negative, participants low in self-esteem accepted it. The authors discuss how these findings shed light on the maintenance of low self-esteem.

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A New pH Oscillator: The Chlorite−Sulfite−Sulfuric Acid System in a CSTR

A new pH oscillator has been discovered involving the system of NaClO2, Na2SO3, and H2SO4 in a continuous-flow stirred tank reactor (CSTR). While ClO2- serves as an oxidant in numerous systems exhibiting nonlinear dynamical behavior, this is the first reported chlorite-based pH oscillator. Large-amplitude oscillations in pH and potential of a platinum electrode were observed over a rather narrow concentration range. Complex dynamical behavior also was observed, including aperiodic oscillations, bistability between steady states, bistability between steady state and oscillatory state, bursting, a possible third steady state, and damped oscillations in batch. Autocatalytic oxidation of HSO3- by ClO2- is a major source of positive feedback in H+. A fast Cl+-transfer reaction between HOCl and SO32- is an important source of negative feedback. Oscillations were also obtained in the presence of Na2CO3, with the dehydration reaction of H2CO3 providing additional negative feedback. Models are proposed to account ...

On the role of local-field effect on optical intersubband saturation and intrinsic bistability in a step quantum well

On the basis of a microscopic integral equation which in a systematic manner incorporates electronic and electromagnetic nonlocalities, optical saturation and intrinsic bistability arising from intersubband transitions in a step quantum well have been studied. It is found that local-field effect plays a key role in the process of the nonlinear interaction between the quantum-well system and pump field and in certain suitable conditions the local-field effect can act as a positive feedback source for generating bistability in the step quantum well system. Also a comparison with local theory is presented.