Academic literature on the topic 'MODIFIED CURRENT FEEDBACKS OPERATIONS AMPLIFIERS'

Conventional Current Feedback Operational Amplifier (CFOA) is not current controllable or not electronically controllable. It is thus of interest to add a current mirror into the CFOA in order to make it current controllable. This modification can be achieved by using Diamond Transistor (DT) instead of going through complicated IC fabrication process. This work applies the modified CFOA in fractional-order proportional integral derivative (PIλDδ) controller. Both simulation and experimental results confirm that the modified CFOA is electronically controllable.

This work presents a low-power biopotential amplifier integrated circuit (IC) for implantable neural recording prosthetic devices which have been implemented using 0.18-[Formula: see text]m CMOS technology. The proposed neural recording amplifier is based on a capacitive-feedback architecture and utilizes a low-power two-stage source-degenerated operational transconductance amplifier (OTA) with a modified current buffer compensation for large open-loop gain, low-noise and wide bandwidth. The designed amplifier achieves a measured gain of 39.2[Formula: see text]dB with a bandwidth between 0.25[Formula: see text]Hz to 28[Formula: see text]kHz, integrated input referred noise of 5.79[Formula: see text][Formula: see text]Vrms and noise efficiency factor of 3.16. The IC consumes 2.4[Formula: see text][Formula: see text]W at 1.2[Formula: see text]V supply and the die area is 0.09[Formula: see text]mm2.

Abstract. To improve high-resolution numerical environmental prediction, it is essential to represent ocean–atmosphere interactions properly, which is not the case in current operational regional forecasting systems used in western Europe. The objective of this paper is to present a new forecast-oriented coupled ocean–atmosphere system. This system uses the state-of-the-art numerical models AROME (cy43t2) and NEMO (v3.6) with a horizontal resolution of 2.5 km. The OASIS coupler (OASIS3MCT-4.0), implemented in the SurfEX surface scheme and in NEMO, is used to perform the communications between models. A sensitivity study of this system is carried out using 7 d simulations from 12 to 19 October 2018, characterized by extreme weather events (storms and heavy precipitation) in the area of interest. Comparisons with in situ and L3 satellite observations show that the fully coupled simulation reproduces the spatial and temporal evolution of the sea surface temperature and 10 m wind speed quantitatively well. Sensitivity analysis of ocean–atmosphere coupling shows that the use of an interactive and high-resolution sea surface temperature (SST), in contrast to actual numerical weather prediction (NWP) where SST is constant, modifies the atmospheric circulation and the location of heavy precipitation. Simulated oceanic fields show a large sensitivity to coupling when compared to the operational ocean forecast. The comparison to two distinct forced ocean simulations highlights that this sensitivity is mainly controlled by the change in the atmospheric model used to drive NEMO (AROME vs. IFS operational forecast), and less by the interactive air–sea exchanges. In particular, the oceanic boundary layer depths can vary by more than 40 % locally, between the two ocean-only experiments. This impact is amplified by the interactive coupling and is attributed to positive feedback between sea surface cooling and evaporation.

Electrons and holes in graphene behave as relativistic charged massless Dirac fermions due to the graphene unique gapless electronic band structure with a linear dispersion law. Dirac plasmons - the quanta of the plasma oscillation of the Dirac electrons - can dramatically enhance the interaction of terahertz (THz) photons with graphene. We have proposed an original current-injection graphene THz laser transistor, demonstrated single-mode THz laser oscillation at low temperatures [1-3], and discovered and demonstrated the THz giant gain enhancement effect by the graphene Dirac plasmons [4-8]. However, further breakthroughs are needed to realize room-temperature high-intensity THz lasing and ultrafast modulation operation for the next generation wireless 6G and 7G communications. In this paper, we will present new ideas on the operating principle and device structures of the THz graphene plasmonic laser transistors with a high radiation intensity and ultrafast modulation capability operating at room temperature. To dramatically improve the quantum efficiency and gain, we utilize the Coulomb drag effect in lateral n+ - i – n - n+ graphene diode/transistor structures with the ballistic injection of the graphene Dirac fermions [9-11]. Such injection strongly modifies the current-voltage characteristics producing “plasmonic gain” in the THz frequency range applicable for THz oscillations and amplifications. This phenomenon is associated with the specifics of the ballistic electron scattering on quasi-equilibrium electrons in graphene. Depending on the device structural parameters (in particular, the gated region length and its electron Fermi energy), the graphene diode/transistor structures can exhibit either S-shaped or monotonic current-voltage characteristics [9]. In the former case, the resulting hysteresis and current filamentation effects can be used for the implementation of the voltage-switching devices. The feedback between the amplified dragged electrons current and the injected ballistic electrons current can lead to the negative THz dynamic conductivity. The self-excitation of the THz plasma oscillations in the gated region enables the realization of the graphene transistor-based sources of THz radiation [11]. To realize ultrafast modulation of lasing intensity/phase, we introduce actively controlling the parity and time-reversal (PT) symmetry [12] of the graphene Dirac plasmons (GDPs) in the dual-grating-gate graphene-channel field effect transistor (DGG-GFET) nanostructures for the ultrafast modulation of the lasing intensity and phase. [13]. The PT symmetry is expressed by a pair of complementary gain and loss elements. This gain–loss balance leads to the exceptional points at the real frequency axis in the exact PT-phase resulting in the extraordinary frequency response of “unidirectionality” [14]. The DGG-GDP metasurface, which consists of a unit cell comprising a pair of gain and loss regions and its periodical arrangement, promotes the GDP instability. The PT symmetry can be controlled (to be held or broken) by altering the gate or drain bias voltages. Our numerical simulations showed that the laser cavity Q values can be dynamically controllable in a DGG-GDP transistor structure [6] demonstrating 100-Gbit/s-class ultrafast modulation capabilities [13]. The authors thank A.A. Dubinov, D. Yadav, T. Watanabe, T. Suemitsu, W. Knap, V. Kachorovskii, and V.V. Popov for their contributions. This work was supported by JSPS-KAKENHI No. 21H04546, and No. 20K20349, Japan. V. Ryzhii, M. Ryzhii, and T. Otsuji, J. Appl. Phys. 101, 083114 (2007). T. Otsuji et al., IEEE J. Sel. Top. Quantum Electron. 19, 8400209 (2013). D. Yadav et al., Nanophoton. 7, 741-752 (2018). A.A. Duvinov el al., J. Phys.: Cond. Matters 23, 145302 (2011). T. Watanabe et al., New J. Phys. 15, 075003 (2013). Y. Koseki et al., Phys. Rev. B 93, 245408 (2016). S. Boubanga-Tombet et al., Phys. Rev. X 10, 031004 (2020). S. Boubanga-Tombet et al., Front. Phys. 9, 726806 (2021). V. Ryzhii et al., Phys. Rev. Appl. 16, 014001 (2021). V. Ryzhii et al., Appl. Phys. Lett. 119, 093501 (2021). V. Ryzhii et al., Physica Status Solidi A 218, 2100535 (2021). M.-A. Miri and A. Alu, Science 363, eaar7709 (2019). T. Otsuji et al., Nanophoton. under review. H. Ramezani and T. Kottos, Phys. Rev. A 82, 04383 (2010). Figure 1

The recent trend in electronics has been towards reducing the size of circuits, a trend which culminated in the development of integrated circuits, but it has been proven impractical to achieve a comparable reduction in the size of inductors because of the relation between the size of inductor and the quality factor. Also inductors are seldom used at low frequencies because at very low frequency the size and weight of inductors become exceedingly large and quality factor becomes very low. Fortunately, active circuits can sometimes synthesize the equivalent of an inductor with high quality factor. In this dissertation, we have presented a modified current feedback operational amplifier (MCFOA), which is more suitable for realizing simulated inductors and active filters. New grounded inductor and floating inductor have been simulated using a minimum number of passive components based on one or two modified current feedback operational amplifiers (MCFOAs) and the result is validated with the implementation of RL high pass filter. To show the flexibility of the proposed MCFOA, a single input three output (SITO) voltage mode filter and three input single output (TISO) voltage mode filters employing a single MCFOA have been simulated using the PSPICE program. In communication, control and instrumentation systems an electrical signal may get altered by many linear or nonlinear transformation caused by the signal processors or transmission system. To recover these distortions of the signal, a system is required that has inverse transfer characteristics of the original system. Inverse filter can correct these distortions because it has frequency response, which is the reciprocal of the frequency response of the system that caused the, distortion. In this dissertation, inverse filters have been designed using both the Modified current feedback operational amplifier (MCFOA) and standard AD844 CFOA. The workability of the proposed inverse filters is demonstrated by PSPICE simulations.