Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Dual voltage automotive electrical system with sub-resonant DC-DC converter

Abstract: An improved dual voltage automotive electrical system in which low voltage loads (19) are powered by a series resonant DC-DC converter (18) operated at a fixed switching frequency below the resonant frequency of its tank circuit. With this arrangement, the converter (18) provides a fixed conversion ratio from the regulated upper system voltage (Vin), and operates with the beneficial attributes of zero current switching and inherent overload protection. In a first embodiment, a transformer (T2) inductively couples the converter tank circuit to the low voltage loads (19), providing full input/output galvanic isolation. In a second embodiment, the converter (18) is configured so that a portion of the power supplied to the low voltage loads (18) is directly coupled from the upper system voltage source (Vin), with the remaining portion being coupled through the converter (18). In either embodiment, the accuracy of the conversion ratio and its load current independence are enhanced by a compounding coil (Ta, Tb) having a load current dependent inductance coupled to the tank circuit.

Current-Voltage Model for Negative Capacitance Field-Effect Transistors

Abstract: In this letter, a semi-analytical current–voltage model for a negative capacitance field-effect transistor (NCFET) with a ferroelectric material ( i.e. , BaTiO3) is proposed. Surface potential ( $\psi _{\mathrm {S}})$ in the channel region is determined first by solving the Landau–Khalatnikov (LK) equation numerically with Poisson’s equation. Then, the drain–current is achieved based on the current continuity equation using $\psi _{\mathrm {S}}$ determined earlier. In addition, by introducing a fitting potential for a given drain–voltage, threshold voltage shift can be captured, resulting in accurate surface potential and drain–current at different gate voltages. We have verified our model using the technology computer-aided design (TCAD)-MATLAB simulation, and our model exhibits an excellent agreement to the simulation results. In addition, the impacts of the ferroelectric thickness and channel doping concentration on the device performance and hysteresis window of NCFET are thoroughly explored.

Voltage reference circuit

Abstract: A voltage reference circuit including a positive temperature coefficient current generator, a negative temperature coefficient current generator, and a first resistor is provided. In the positive temperature coefficient current generator, two transistors are operated in the weak inversion region, and a second resistor is connected in series between the gates of the two transistors. The second resistor employs the characteristic that a transistor operated in weak inversion region acts like a bipolar junction transistor to generate a positive temperature coefficient current. The negative temperature coefficient current generator generates a negative temperature coefficient current in response to a negative temperature coefficient voltage drop on a third resistor. The positive temperature coefficient current and the negative temperature coefficient current flow through the first resistor together, thus producing a stable reference voltage.

Controlling a bidirectional dc-to-dc converter

Abstract: A system and method for regulating power flow and limiting inductor current in a bidirectional direct current (DC)-to-DC converter is provided In one aspect, a feedback circuit is provided to control power flow and/or limit inductor current based on the input/output voltage and/or current conditions in the bidirectional DC-DC converter During a boost mode of operation, the duty cycle of a low-side switch within the bidirectional DC-DC converter is reduced, based on an analysis of the high-side voltage and positive inductor current Further, during a buck mode of operation, the duty cycle of the low-side switch is increased, based on an analysis of the low-side voltage and negative inductor current Moreover, the duty cycle of the low-side switch is adjusted, such that, the high-side voltage, low-side voltage and inductor current (in both directions) do not exceed preset threshold and the bidirectional DC-DC converter returns to a steady state

Effect of hysteretic and non-hysteretic negative capacitance on tunnel FETs DC performance.

Abstract: This work experimentally demonstrates that the negative capacitance effect can be used to significantly improve the key figures of merit of tunnel field effect transistor (FET) switches. In the proposed approach, a matching condition is fulfilled between a trained-polycrystalline PZT capacitor and the tunnel FET (TFET) gate capacitance fabricated on a strained silicon-nanowire technology. We report a non-hysteretic switch configuration by combining a homojunction TFET and a negative capacitance effect booster, suitable for logic applications, for which the on-current is increased by a factor of 100, the transconductance by 2 orders of magnitude, and the low swing region is extended. The operation of a hysteretic negative capacitance TFET, when the matching condition for the negative capacitance is fulfilled only in a limited region of operation, is also reported and discussed. In this late case, a limited improvement in the device performance is observed. Overall, the paper demonstrates the main beneficial effects of negative capacitance on TFETs are the overdrive and transconductance amplification, which exactly address the most limiting performances of current TFETs.