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.

Ultra-low-power DLMS adaptive filter for hearing aid applications

Abstract: We present an ultra-low-power, delayed least mean square (DLMS) adaptive filter operating in the subthreshold region for hearing aid applications. Subthreshold operation was accomplished by using a parallel architecture with pseudo nMOS logic style. The parallel architecture enabled us to operate the system at a lower clock rate and reduced supply voltage while maintaining the same throughput. Pseudo nMOS logic operating in the subthreshold region (subpseudo nMOS) provided better power-delay product than subthreshold CMOS (sub-CMOS) logic. Simulation results show that the DLMS adaptive filter can operate at 22 kHz using a 400-mV supply voltage to achieve 91% improvement in power compared to a nonparallel, CMOS implementation. To validate the robust operation of subthreshold logics, a 0.35 /spl mu/m, 23.1 kHz, 21.4 nW, 8/spl times/8 carry save array multiplier test chip was fabricated where an adaptive body biasing scheme is used for compensating process, supply and temperature variations. The test chip showed stable operation at a supply voltage of 0.30 V, which is even lower than the threshold voltages of the pMOS (0.82 V) and nMOS (0.67 V) transistors.

Threshold voltage modeling and the subthreshold regime of operation of short-channel MOSFETs

Abstract: An analytical model for the subthreshold regime of operation of short-channel MOSFETs is presented, and expressions for the threshold-voltage shift associated with the drain-induced barrier lowering (DIBL) caused by the application of a drain bias are developed. The amount of drain-bias-induced depletion charge in the channel is estimated, and an expression for the distribution of this charge along the channel is developed. From this distribution, it is possible to find the lowering of the potential barrier between the source and the channel, and the corresponding threshold-voltage shift. The results are compared with experimental data for deep-submicrometer NMOS devices. Expressions for the subthreshold current and for a generalized unified charge control model (UCCM) for short-channel MOSFETs are presented. The theory is applicable to deep-submicrometer devices with gate lengths larger than 0.1 mu m. The model is suitable for implementation in circuit simulators. >

Synaptic noise improves detection of subthreshold signals in hippocampal CA1 neurons.

Abstract: Stochastic resonance (SR) is a phenomenon whereby the detection of a low-level signal is enhanced in a nonlinear system by the introduction of noise. Studies of the effects of SR in neurons have suggested that noise could play a prominent role in improving detection of small signals. Most experimental SR research has focused on the role of noise in sensory neurons using physiological stimuli. Computer simulations show that signal detection in hippocampal neurons is improved by the addition of physiological levels of noise applied extracellularly to synaptic inputs. These results were confirmed experimentally. We now report that endogenous noise sources can also improve signal detection. The noise source was generated by modulating the random synaptic activity on the apical dendrites of CA1 cells in rat hippocampal slices using subthreshold cathodic current. Intracellular recordings of CA1 cells showed that even small increases of synaptic noise are able to greatly improve the detection of an independent, synaptic, subthreshold stimulus as predicted by the simulations. The noise variance in the CA1 cell was compared with the resting variance and with variance changes caused by several endogenous noise sources. In all cases, the increased noise variance was well within the physiological range. These results were supplemented and analyzed with a CA1 computer model. The improved signal detection with small amounts of endogenous noise suggests that the diverse inputs to CA1 are able to improve detection of subthreshold synaptic signals and could provide a means to modulate detection of specific inputs in the hippocampus.

A Full-Range Drain Current Model for Double-Gate Junctionless Transistors

Abstract: A drain current model available for full-range operation is derived for long-channel double-gate junctionless transistors. Including dopant and mobile carrier charges, a continuous 1-D charge model is derived by extending the concept of parabolic potential approximation for the subthreshold and the linear regions. Based on the continuous charge model, the Pao-Sah integral is analytically carried out to obtain a continuous drain current model. The proposed model is appropriate for compact modeling, because it continuously captures the phenomenon of the bulk conduction mechanism in all regions of device operation, including the subthreshold, linear, and saturation regions. It is shown that the model is in complete agreement with the numerical simulations for crucial device parameters and all operational voltage ranges.

Connection between asymptotic normalization coefficients, subthreshold bound states, and resonances

Abstract: We present here useful relations showing the connection between the asymptotic normalization coefficient (ANC) and the fitting parameters in K- and R-matrix theory methods which are often used when analyzing low energy experimental data. It is shown that the ANC of a subthreshold bound state defines the normalization of both direct radiative capture leading to this state and resonance capture in which the state behaves like a subthreshold resonance. A determination of the appropriate ANC(s) thus offers an alternative method for finding the strength of these types of capture reactions, both of which are important in nuclear astrophysics.