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.

Explicit compact model for symmetric double-gate MOSFETs including solutions for small-geometry effects

Abstract: A physics-based compact model including short-channel effects (SCEs) is presented for undoped (or lightly doped) symmetric double-gate (DG) MOSFETs. Our approach allows an accurate description of the device behavior down to 60 nm with a simple set of equations. It is shown that the subthreshold current, the threshold voltage roll-off and the DIBL predicted by the analytical solution are in close agreement with 2-D numerical simulations performed with Atlas. The mobility degradation due to both transverse and longitudinal fields is taken into account but the channel length modulation (saturation regime) is not addressed in this paper. In order to demonstrate that the model is well-suited for circuit simulation, the results of the dynamic model based on an explicit formulation of the mobile charge density are also presented.

A Novel Tunnel FET Design With Stacked Source Configuration for Average Subthreshold Swing Reduction

Abstract: In this paper, a novel heterostacked tunnel FET (HS-TFET) is proposed for steeper average subthreshold swing (SS). Different from conventional TFETs, HS-TFETs owns a stacked source configuration consisting of an upper source layer with a relatively larger bandgap material and an underlying source layer with smaller bandgap materials. Since smaller bandgap materials exhibit much higher band-to-band tunneling efficiency, the underlying layer of HS-TFET could provide extra drain current increment with increasing gate voltage, and thus effectively improve the subthreshold characteristics for steeper average SS. The simulation results show that the proposed Si–Ge-based HS-TFET can achieve much steeper average SS (25 mV/decade) than conventional Si TFET (42 mV/decade), exhibiting more than one decade higher I60 without leakage current degradation.

Paresthesia-Free High-Density Spinal Cord Stimulation for Postlaminectomy Syndrome in a Prescreened Population: A Prospective Case Series.

Abstract: Objective Spinal cord stimulation (SCS) traditionally is thought to require paresthesia, but there is evidence that paresthesia-free stimulation using high-density (HD) parameters might also be effective. The purpose of this study is to evaluate relative effectiveness of conventional, subthreshold HD, and sham stimulation on pain intensity and quality of life. Methods Fifteen patients with response to conventional stimulation (60 Hz/350 μsec) were screened with a one-week trial of subthreshold HD (1200 Hz/200 μsec/amplitude 90% paresthesia threshold) and enrolled if there was at least 50% reduction on visual analog scale (VAS) for pain. Subjects were randomized into two groups and treated with four two-week periods of conventional, subthreshold HD, and sham stimulation in a randomized crossover design. Results Four of 15 patients responded to subthreshold HD stimulation. Mean VAS during conventional, subthreshold HD, and sham stimulation was 5.32 ± 0.63, 2.29 ± 0.41, and 6.31 ± 1.22, respectively. There was a significant difference in pain scores during the blinded crossover study of subthreshold HD vs. sham stimulation (p < 0.05, Student's t-test). Post hoc analysis revealed that subjects reported significantly greater attention to pain during conventional stimulation compared with subthreshold HD stimulation (p < 0.05, Student's t-test). All subjects reported a positive impression of change for subthreshold HD stimulation compared with conventional stimulation, and there was a trend toward greater likelihood for response to subthreshold HD stimulation in comparison with sham stimulation (p = 0.07, Fisher's exact test). At the end of the trial, all subjects elected to continue to receive subthreshold HD stimulation rather than conventional stimulation. Conclusions Paresthesia are not necessary for pain relief using commercially available SCS devices, and may actually increase attention to pain. Subthreshold HD SCS represents a viable alternative to conventional stimulation among patients who are confirmed to have a clinical response to it.

Improved Conductance Linearity and Conductance Ratio of 1T2R Synapse Device for Neuromorphic Systems

Abstract: We report on a 1-transisor/2-resistor (1T2R) synapse device with improved conductance linearity and conductance ratio under an identical pulse condition for hardware neural networks with high pattern-recognition accuracy. Utilizing an additional series-connected resistor, the conductance linearity of a synapse device was significantly improved owing to the reduced initial voltage drop on an resistive RAM (RRAM) device during depression conditions. Moreover, to maximize the conductance ratio of a synapse device, we utilized a steep subthreshold region of an MOSFET by a parallel connection of an RRAM and a transistor. A small change in voltage on the RRAM directly controlled the gate bias of the MOSFET, which causes a large change in the drain current. Compared with a conventional RRAM synapse device, the 1T2R synapse device shows an improved conductance linearity and conductance ratio ( $> \times 100$ ). Finally, we confirmed an excellent classification accuracy by using a neural network simulation based on a multilayer perceptron.

Enhancement of neural synchronization in computational models of ventral cochlear nucleus bushy cells

Abstract: Ventral cochlear nucleus (VCN) bushy cells, especially globular bushy cells (GBCs), show enhanced synchronization to low-frequency tones (<1 kHz) when compared to auditory nerve (AN) fibers. Joris and colleagues (J. Neurophysiol. 71:1022, 1994) interpreted the enhanced synchronization as implying that GBCs receive multiple AN inputs which are individually subthreshold, so that the enhancement results from the necessity for coincidence of input spikes in order to produce an output spike. By contrast, in a previous modeling study, we concluded that high-BF GBCs must receive suprathreshold inputs in order that their spike trains be irregular and in order that they synchronize strongly in the midfrequency range (1-5 kHz). In this study, we reconsider the modeling results in an attempt to account for enhanced synchrony in models which display all the properties of bushy cells; the principal variables studied are the number and strength of synaptic inputs. A simple shot-noise threshold model displays enhanced synchronization at 500 Hz with either subthreshold or suprathreshold inputs. A membrane-conductance model, which accurately reproduces bushy-cell electrical characteristics, displays enhanced synchronization at low frequencies with a variety of input configurations. These configurations differ in their spontaneous activity, regularity, PST histogram shape, and mid-frequency phase-locking. Models with all subthreshold or all suprathreshold inputs each match some aspects of GBC behavior, but neither model reproduces all aspects: subthreshold models phase-lock more weakly at mid-frequencies than almost all the GBC data and suprathreshold models have inappropriate PST histogram shapes and spontaneous rates that are too high. A model which better reproduces average GBC data has suprathreshold inputs combined with a tonic inhibitory input. However, the modeling results, taken as a whole, suggest that there must be subclasses of GBCs with different arrangements of synaptic input, including both subthreshold and suprathreshold inputs.