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Subthreshold conduction

About: Subthreshold conduction is a research topic. Over the lifetime, 6343 publications have been published within this topic receiving 131957 citations. The topic is also known as: Subthreshold leakage.


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Journal ArticleDOI
22 Jan 2010
TL;DR: This paper explores how design in the moderate inversion region helps to recover some of that lost performance, while staying quite close to the minimum-energy point, and introduces a pass-transistor based logic family that excels in this operational region.
Abstract: Operation in the subthreshold region most often is synonymous to minimum-energy operation. Yet, the penalty in performance is huge. In this paper, we explore how design in the moderate inversion region helps to recover some of that lost performance, while staying quite close to the minimum-energy point. An energy-delay modeling framework that extends over the weak, moderate, and strong inversion regions is developed. The impact of activity and design parameters such as supply voltage and transistor sizing on the energy and performance in this operational region is derived. The quantitative benefits of operating in near-threshold region are established using some simple examples. The paper shows that a 20% increase in energy from the minimum-energy point gives back ten times in performance. Based on these observations, a pass-transistor based logic family that excels in this operational region is introduced. The logic family operates most of its logic in the above-threshold mode (using low-threshold transistors), yet containing leakage to only those in subthreshold. Operation below minimum-energy point of CMOS is demonstrated. In leakage-dominated ultralow-power designs, time-multiplexing will be shown to yield not only area, but also energy reduction due to lower leakage. Finally, the paper demonstrates the use of ultralow-power design techniques in chip synthesis.

391 citations

Journal ArticleDOI
L.D. Yau1
TL;DR: A simple expression for the threshold voltage of an IGFET is derived from a charge conservation principle which geometrically takes into account two-dimensional edge effects in this paper, which is valid for short and long-channel lengths.
Abstract: A simple expression for the threshold voltage of an IGFET is derived from a charge conservation principle which geometrically takes into account two-dimensional edge effects. The expression is derived for zero drain voltage and is valid for short and long-channel lengths. The dependence of the threshold voltage on the source and drain diffusion depth, r j , and channel length, L , is explicitly given. In the limit, L / r j → ∞, the threshold voltage equation reduces to the familiar expression for the long-channel case. The theory is compared with the measured threshold voltages on IGFET's fabricated with 1·4, 3·8 and 7·4 μm channel lengths. The dependence of the threshold voltage under backgate bias voltages ranging from zero to breakdown agrees closely with the theory.

378 citations

Journal ArticleDOI
01 Dec 2002
TL;DR: In this paper, single-wall carbon nanotube field effect transistors (CNFETs) operating at gate and drain voltages below 1V were investigated and it was shown that CNFET operation is controlled by Schottky barriers (SBs) in the source and drain region instead of by the nanotubes itself.
Abstract: Presents experimental results on single-wall carbon nanotube field-effect transistors (CNFETs) operating at gate and drain voltages below 1V. Taking into account the extremely small diameter of the semiconducting tubes used as active components, electrical characteristics are comparable with state-of-the-art metal oxide semiconductor field-effect transistors (MOSFETs). While output as well as subthreshold characteristics resemble those of conventional MOSFETs, we find that CNFET operation is actually controlled by Schottky barriers (SBs) in the source and drain region instead of by the nanotube itself. Due to the small size of the contact region between the electrode and the nanotube, these barriers can be extremely thin, enabling good performance of SB-CNFETs.

375 citations

Journal ArticleDOI
TL;DR: It is speculated that the tendency of the neurons to generate voltage signals at a certain frequency (as a result of the subthreshold oscillations) and to preferentially respond to inputs arriving at the same frequency (the resonance behaviour) promotes population activity at that preferred frequency.
Abstract: 1. Intracellular recordings were made from neurons in slices from guinea-pig frontal cortex. In 50% of the cells, sustained subthreshold voltage oscillations were evoked by long (> 6 s) depolarizing pulses. The peak-to-peak amplitude of these oscillations was less than 5 mV and the frequency was voltage dependent, increasing with depolarization from 4 (near rest) to 20 Hz (at 30 mV depolarization). 2. The impedance-frequency relationship of both oscillating and non-oscillating cells was studied by intracellular injection of sinusoidal current with linearly changing frequency. In most cells, a peak in the impedance magnitude (resonant behaviour) was observed at depolarized levels. The frequency of the peak impedance (peak frequency) increased with depolarization from 3 (near rest) to 15 Hz (at 30 mV depolarization). 3. Application of TTX (10(-6) M) significantly decreased the impedance magnitude near the peak frequency. The subthreshold oscillations, however, as well as the action potentials, were fully blocked by TTX. On the other hand, TEA (15 mM) and Cs+ (5 mM) abolished both the subthreshold oscillations and the resonant behaviour. Replacing Ca2+ with Co2+ (5 mM) or Ni2+ (1 mM) did not abolish the subthreshold oscillations. The peak in the frequency-response curve was only slightly reduced. 4. An isopotential membrane model, consisting of a leak current, a fast persistent sodium current, a slow non-inactivating potassium current (with the kinetics of the M-current) and membrane capacitance, is sufficient to produce both voltage oscillations and resonant behaviour. The kinetics of the K+ current by itself is sufficient to produce resonance behaviour. The Na+ current amplifies the peak impedance magnitude and is essential for the generation of subthreshold oscillation. The model correctly predicted the behaviour of the frequency response before and after TTX and TEA application, as well as the relation between the expected passive impedance and the experimental impedance. 5. We speculate that the tendency of the neurons to generate voltage signals at a certain frequency (as a result of the subthreshold oscillations) and to preferentially respond to inputs arriving at the same frequency (the resonance behaviour) promotes population activity at that preferred frequency.

374 citations

Proceedings ArticleDOI
08 Dec 2002
TL;DR: The I-MOS as discussed by the authors uses modulation of the breakdown voltage of a gated p-i-n structure in order to switch from the OFF to the ON state and vice versa.
Abstract: One of the "fundamental" problems in the continued scaling of MOSFETs is the 60 mV/decade room temperature limit in subthreshold slope. In this paper, we report initial studies on a new kind of transistor, the I-MOS. The I-MOS uses modulation of the breakdown voltage of a gated p-i-n structure in order to switch from the OFF to the ON state and vice versa. Since impact-ionization is an abrupt function of the electric field (or the carrier energy), simulations show that the device has a subthreshold slope much lower than kT/q. Simulations also show that it is indeed possible to make complementary circuits with switching speeds comparable to or exceeding CMOS. Experimental results on a silicon based prototype verify the basic concept and show very steep subthreshold slopes with high speed turn-on and turn-off. Lower bandgap materials are also being investigated to reduce the value of the breakdown voltage and permit lower voltage operation.

367 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023153
2022349
2021172
2020196
2019242
2018272