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Low-power circuits often employ dynamic voltage scaling and energy harvesting. Such circuits need a power management unit that can convert the voltage source to a wide range of target voltages with high efficiency. Targeting such a power management unit, this paper presents a reconfigurable architecture of switched capacitor (SC) voltage converter. It introduces a design optimization methodology that can determine trade-off among design parameters to meet the goal. The proposed converter employs a reconfigurable topology with four capacitors. It provides 11 conversion ratios: 6 step-down and 5 step-up ratios supporting wide input/output voltage range. An analytical model for the output impedance of the proposed reconfigurable SC topology is presented. Using the model, the proposed optimization methodology can minimize the total power dissipation. To validate the proposed architecture and optimization methodology, the converter has been implemented in a 130-nm CMOS process using integrated capacitors of total size 2.2 nF. Simulation results show that the optimized converter circuit achieves an efficiency range from 83.41% to 74.69% for a load current of $100~\mu \text{A}$ .

This paper describes the development of new configurations for flip-flops which are based on a microthyristor as a storage element, the NMOS transistor as a series switch or a driver and a high pull-up resistor. The performance of these flip-flops is analysed, using a PSPICE simulator. These devices perform well with regard to speed and power consumption and are more compact because of the use of the microthyrister.

In this paper, a new microthyristor structure suitable for microelectronics applications has been introduced. A suitable technology for its implementation has been chosen. The microthyristor has been designed and its performance has been simulated. The device showed superior performance concerning the switching times and the power dissipation in addition to controllability of its S-curve. During the development of this work, we introduced some new concepts such as doping-engineered devices, thyristor turn-off by shunting its cathode junction, and power consumption reduction by realizing high resistances. The basic requirements and some conditions are put together for successful launch of the microthyristor in microelectronics.

In this short paper we introduce new complementary BiCMOS buffers employing multidrain/multi-collector structures. These circuits offer near rail-to-rail output voltage, less circuit complexity, less process complexity, and high performance at scaled down power supply voltages (

DC characterization of n MOS inverters is carried out from liquid helium up to room temperatures. The benefits resulting from the low temperature operation on the performances of the n MOS inverter are studied. In particular, the improvement of the switching gain at low temperature is pointed out. Moreover, the relative noise margin is found to increase significantly at low temperature (≈50K). The possibility to operate the n MOS inverter at low temperature while reducing the supply voltage and in turn the power consumption is emphasized.

A study of flicker noise in MOS transistors operated in the linear and non linear regions at room and liquid helium temperatures is proposed. Besides, a theoretical analysis of the drain current noise characteristics is developed in the framework of the mobility fluctuation model as well as of the carrier number fluctuation model. It is shown experimentally that a close correlation between the drain current spectral density and the transconductance squared dependencies with gate voltage (or drain current) and drain voltage is observed in our devices both at room and liquid helium temperatures. Therefore, it is concluded that the carrier number fluctuation model is not only applicable to MOS devices operated at room temperature but also at liquid helium temperature in ohmic and non ohmic regimes. In addition, peculiarities of the drain current noise related to the appearance of a kink effect at liquid helium temperature in the saturation current characteristics are also discussed.

An analysis of silicon metal‐oxide‐semiconductor (MOS) transistor operation at liquid‐helium temperature is presented. More specifically, analytical models providing the drain current and transconductance characteristics in the linear and nonohmic regions are established in the presence of source‐drain series resistances. These models, which rely on a specific mobility law for very low temperature, enable a good description of MOS transistor operation to be obtained. They permit the understanding and the prediction of the effects of source‐drain series resistance both in the linear and nonlinear regions. Furthermore, they allow a suitable parameter extraction method to be developed for the liquid‐helium temperature range. In addition, peculiarities of the drain voltage dependence of the mobility at low longitudinal electric field are also pointed out and empirically accounted for in the modeling of the output characteristics.

A numerical model for the ohmic operation of depletion-mode MOS transistors operated at very low temperature is presented. This model which is based on a quantum treatment of the accumulation layer and on a specific mobility law enables a good modelling of the transfer characteristics Id(Ug) and gm(Ug) to be obtained from weak to strong accumulation. An analytical version of this model is also derived for the strong accumulation region above flat-band. This model relies on simple analytical expressions which contain only three parameters i.e. the flat-band voltage Vfb, the maximum mobility μm and the mobility attenuation factor θlt. Moreover, a method for the extraction of the depletion-mode MOSFET parameters based on the plot of the I/g(Ug) characteristics is presented. Ein numerisches Modell fur den ohmschen Bereich von MOS-Verarmungstransistoren bei sehr tiefen Temperaturen wird angegeben. Dieses Modell, das auf einer Quantenberechnung der Akkumulationsschicht und einem spezifischen Beweglichkeitsgesetz beruht, erlaubt eine gute Modellierung der Transfercharakteristiken Id(Ug) und gm(Ug) im Bereich zwischen schwacher und starker Akkumulation. Eine analytische Version dieses Modells wird auch fur den starken Akkumulationsbereich oberhalb Flachband abgeleitet. Dieses Modell beruht auf einfachen analytischen Ausdrucken, die nur drei Parameter, die Flachbandspannung Ufb, die Maximalbeweglichkeit μm und den Beweglichkeitsdampfungsfaktor θlt enthalten. Daruberhinaus wird eine Methode zur Bestimmung der MOSFET-Verarmungsparameter angegeben, die auf der Auftragung von I/g (Ug)-Charakteristiken beruht.

The performance and the physical properties of SIMOX (separation by implantation of oxygen) MOS transistors are studied from room to liquid helium temperatures with particular emphasis on the behavior of carrier mobility, threshold voltage, subthreshold swing, leakage current, and kink effect. Various SIMOX substrates, such as partially depleted films annealed at low or high temperature and ultrathin films (100 nm), are analyzed and compared. Enhancement- and depletion-mode devices with different doping levels, channel lengths, and geometries are considered. The front and back channels are activated independently in order to assess the electrical quality of both interfaces. Comparison with bulk Si transistors reveals a number of interesting features of SIMOX devices, which are explained using comprehensive models. The advantages of low-temperature operation of SIMOX transistors are related to the decrease in subthreshold swing and leakage, increase in mobility, and reasonable shift of the threshold voltage. The performance of ultra-thin-film devices is excellent over the whole range or temperatures, whereas partially depleted transistors exhibit optimum performance at 77 K. >

An analysis of the kink effect in MOS transistors that provides a comprehensive view of the kink effect in bulk silicon MOSFETs and SOI devices is presented. This analysis enables a quantitative description of the excess drain current to be obtained for room and liquid-helium temperatures. In particular, it is found that the kink effect in a MOS transistor can be simply modeled by a body effect. >

Flicker noise in MOS transistors operated in the linear and non linear regions is studied at room and liquid helium temperatures. A theoretical analysis of the drain current noise is conducted within the mobility and carrier number fluctuation models. A close correlation between the drain current noise and the transconductance squared dependencies with gate and drain voltages is found experimentally both at room and liquid helium temperatures. It is concluded that the carrier number fluctuation model is suitable for the interpretation of our data at room and liquid helium temperatures in ohmic and non ohmic regimes. Peculiarities of the drain current noise in the kink effect region are also discussed.

The interface state density of silicon metal‐oxide‐semiconductor (MOS) transistors operated at room, liquid‐nitrogen, and liquid‐helium temperatures is investigated using the conventional subthreshold slope technique. The magnitude of the interface state density found of the order of 1013–1014/eV cm2 at liquid‐helium temperature, suggests that such states correspond to the localized states situated in the band tails below the mobility edge of the two‐dimensional subband. Moreover, the interface state densities found by the subthreshold slope have been confirmed using the dynamic transconductance technique.

A study of the effective mobility in silicon MOS inversion and accumulation layers at liquid helium temperature is reported. It is demonstrated, using MOS devices of various technologies, that theeffective mobility, =eff, at liquid helium temperature can be represented by a bell-shaped function of the inversion (or accumulation) charge Qn which has the generic form=eff(Qn) = 2=m/Qn/Qm+QmQnwhere =m is the maximum mobility and Qm a critical charge of the order of 1–3 × 1012q/cm2, which are parameterised functions of the bulk charge in the case of enhancement-mode devices. This mobility law, which can be considered as a universal feature of the transport at the Si–SiO2 interface, enables an analytical modelling of enhancement and depletion mode MOS transistors to be obtained at liquid helium temperature.

An original method for MOSFET parameter extraction is presented as a function of temperature. This method, which relies on combining drain current and transconductance transfer characteristics, enables reliable values of the threshold voltage and mobility parameters.

A numerical model for the non ohmic MOSFET operation at liquid helium temperature is presented. This model which takes into account the basic requirements for device modelling at very low temperature (i.e. energy quantization in the inversion layer, specific mobility law, carrier velocity saturation) allows a good description of the drain current characteristics vs drain voltage to be obtained for various gate voltages. Moreover, an analytical approximation of this model is also proposed for the MOSFET operation in strong inversion condition.

A study of the normalized drain current spectral density SId/I2d as a function of drain current has been carried out on n channel metal‐oxide‐semiconductor transistors at very low (4 K), low (77 K), and room temperatures. It is demonstrated experimentally that the drain current dependence of SId/I2d is strongly correlated to that of the transconductance‐current ratio squared (gm/Id)2. This result clearly shows that the carrier‐number fluctuation model is applicable not only at room temperature but also at low and very low temperatures. Therefore, it is proved that the mobility fluctuation model is inadequate for the interpretation of our flicker noise data.

An analytical model of the kink effect in MOS transistors is proposed. This model procures a comprehensive view of the kink effect in bulk silicon MOSFETs and, subsequently, in SOI devices. It is shown both experimentally and theoretically that the excess drain current induced by the kink effect is proportional to the body transconductance of the device operated at room as well as liquid helium temperatures.