Differential Gain Research Articles

On the Sizing of CMOS Operational Amplifiers by Applying Many-Objective Optimization Algorithms

In CMOS integrated circuit (IC) design, operational amplifiers are one of the most useful active devices to enhance applications in analog signal processing, signal conditioning and so on. However, due to the CMOS technology downscaling, along the very large number of design variables and their trade-offs, it results difficult to reach target specifications without the application of optimization methods. For this reason, this work shows the advantages of performing many-objective optimization and this algorithm is compared to the well-known mono- and multi-objective metaheuristics, which have demonstrated their usefulness in sizing CMOS ICs. Three CMOS operational transconductance amplifiers are the case study in this work; they were sized by applying mono-, multi- and many-objective algorithms. The well-known non-dominated sorting genetic algorithm version 3 (NSGA-III) and the many-objective metaheuristic-based on the R2 indicator (MOMBI-II) were applied to size CMOS amplifiers and their sized solutions were compared to mono- and multi-objective algorithms. The CMOS amplifiers were optimized considering five targets, associated to a figure of merit (FoM), differential gain, power consumption, common-mode rejection ratio and total silicon area. The designs were performed using UMC 180 nm CMOS technology. To show the advantage of applying many-objective optimization algorithms to size CMOS amplifiers, the amplifier with the best performance was used to design a fractional-order integrator based on OTA-C filters. A variation analysis considering the process, the voltage and temperature (PVT) and a Monte Carlo analysis were performed to verify design robustness. Finally, the OTA-based fractional-order integrator was used to design a fractional-order chaotic oscillator, showing good agreement between numerical and SPICE simulations.

Novel Rectangular-Ring Vertex Double-Bar Slow Wave Structure for High-Power High-Efficiency Traveling-Wave Tubes

A novel rectangular-ring vertex double-bar (RRVDB) slow wave structure (SWS) is proposed to develop high-power high-efficiency traveling-wave tube (TWT). The remarkable advantages of this novel slow wave circuit are flatter dispersion and significantly larger interaction impedance in comparison with the circular ring double-bar (RDB) SWS. The particle-in-cell simulation of RRVDB TWT shows that, at beam voltage of 25.1 KV, beam current of 0.2 A, the maximum output power of 581.2 W, corresponding to differential small-signal gain of 0.366 dB/mm and electron efficiency of 11.57%, can be obtained for operating frequency of 34.5 GHz; the output power, gain, and electron efficiency of RRVDB TWT are considerably improved compared with RDB TWT. At the same time, size reduction and bandwidth extension are also achieved for the RRVDB TWT.

Negative capacitance FETs for energy efficient and hardware secure logic designs

Negative capacitance field effect transistors (NCFETs) have attracted good attention for energy efficient circuit designs. However, there are no clear design insights with NCFET based circuit designs for energy efficient and hardware secure applications. However, the lack of clear design insights make energy efficient and hardware secure NCFET circuit design more challenging. This paper presents important design insights and scope of NCFETs for energy efficient and hardware secure logic design at scaled supply voltages. Initially, NCFET device characteristics have been analyzed by varying the ferroelectric layer thickness (tfe) to identify optimum device performance window. At 40 nm technology node, NCFET device demonstrates enhanced characteristics for logic design with tfe in the range of 3 nm–5 nm due to steep subthreshold swing characteristics. NCFET with tfe of 5 nm exhibits 1.22 × higher ON current, 66 × lower leakage current and a SS of 50mV/dec compared to baseline MOSFET (tfe = 0 nm). Further, NCFET based static complementary inverter design exhibits better performance and higher energy efficiency compared to baseline MOSFET. NCFET inverter with tfe of 3 nm achieves optimum performance in terms of voltage transfer characteristics, differential gain, and noise margins. In addition, NCFET with tfe of 3 nm shows minimum energy consumption with the different supply voltages in the range of 0.6–0.8 V. Moreover, NCFET based buffer, logic gates and half-adder designs with tfe of 3 nm achieve approximately 3 × lower energy consumption compared to baseline designs. Apart from this, the NCFET designs exhibit 2 × higher ON current variations, 12 × higher inverter delay variations, and 3.1 × higher ring oscillator frequency variations compared to baseline designs against 5% process parameter variations at a supply voltage of 0.5 V. With the higher variations resulted from ferroelectric layer, NCFET demonstrate the potential and suitability towards the design of hardware security primitives like physically unclonable function (PUF) and true random number generator (TRNG).

Erbium-doped circular photonic crystal fiber design for the amplification of 20 OAM modes

We propose a fiber design consisting of ring-shaped erbium-doped core surrounded by circularly arranged holes of varying radius in fused silica glass to amplify higher-order orbital angular momentum (OAM) modes. We numerically demonstrate simultaneous amplification of 20 OAM modes ( l = 5 , 6, 7, 8, 9) with more than 20 dB gain at 1550 nm wavelength while having differential modal gain of 0.12 dB. We also demonstrate amplification of modes over the C-band with gain excursion of less than 2 dB, differential modal gain of less than 0.2 dB, and noise figure less than 4.2 dB. The proposed erbium-doped fiber amplifier would be useful in high-data-rate space-division multiplexing optical-communication systems.

Impact of the Sampling Period on the Design of Digital PID Controllers

The impact of the sampling period on the parameterization of a digital PID controller in the frequency domain is attempted using three different digital approximations of the integral action. The controller is implemented in the industrial process of regulation of the cement sulphates in the cement mill outlet. The maximum sensitivity, Ms, has been utilized as a main robustness criterion. For the same Ms, proportional and differential gain, a rise of the sampling period leads to a decrease of the integral gain ki for all the three approximations. For the same sampling period, the function between proportional and integral gain differs for the three approximations studied. If the design satisfies two criteria simultaneously, maximum sensitivity and phase margin in the current study, then the permissible PID gains zone becomes narrower.

Amplification of 14 orbital angular momentum modes in ring-core erbium-doped fiber with high modal gain.

We propose and demonstrate an orbital angular momentum (OAM) fiber amplifier supporting 14 OAM modes based on a fabricated ring-core erbium-doped fiber (RC-EDF) with a tailored erbium-doped profile. Theoretical analyses and numerical simulations suggest that the proposed RC-EDF provides relatively uniform gain larger than 20 dB for all 14 modes. With a core pump configuration, we experimentally characterize the performance of the RC-EDF-assisted OAM fiber amplifier, which can acquire a high modal gain up to 33.4 dB and low differential modal gain less than 1.8 dB at the wavelength of 1550 nm. The obtained results indicate successful implementation of the RC-EDF-assisted OAM fiber amplifier for 14 OAM modes with favorable performance.

Few-mode polymer optical waveguide amplifier for mode-division multiplexed transmission.

We propose a few-mode erbium-ytterbium codoped polymer optical waveguide amplifier employing mode-selective photonic lanterns capable of multiplexing and demultiplexing. A reconfigurable pump configuration scheme is adopted to balance the modal gain per mode. A square few-mode waveguide amplifier supporting LP01, LP11a, and LP11b modes is designed and fabricated. The crosstalk effect and modal profiles are characterized. An average gain of 10.4 dB per mode is obtained in a 1.5 cm waveguide at 1555 nm through pumping of the LP01 mode at 320 mW and the LP21b mode at 120 mW at 976 nm. The ultralow differential modal gain is 0.4 dB. In addition, simultaneously amplified LP01, LP11a, and LP11b modes are also demonstrated across the whole C-band with low noise figures. To the best of our knowledge, this is the first report of an experimental realization of a few-mode optical waveguide amplifier.

Third- and fourth-order orbital angular momentum multiplexed amplification with ultra-low differential mode gain.

In this Letter, a ring-core erbium-doped fiber (RC-EDF), with a two-layer erbium-doped structure, supporting up to the fourth-order orbital angular momentum (OAM) mode was designed and fabricated for the OAM mode multiplexed amplification. Using the RC-EDF, the amplification of the third- and fourth-order OAM modes with an ultra-low differential mode gain (DMG) has been demonstrated by observing both the modal intensity and phase distribution and measuring the modal gain under the fundamental mode core pumping. The measured average gain of four modes' (OAM±3,1 and OAM±4,1) multiplexed amplification is >19dB, covering the C band, and the DMG is <1dB. Additionally, the gains of two conjugate OAM modes are almost the same under different pump power, regardless of whether they are amplified simultaneously or separately.

Relative intensity noise and intrinsic properties of RF mounted interband cascade laser

Interband cascade lasers are semiconductor lasers emitting in the mid-infrared domain but relying on interband transitions, contrary to their intersubband counterparts, quantum cascade lasers. Our experimental study of the relative intensity noise in a multi-mode interband cascade laser at 4.1 μm shows that the room-temperature structure exhibits a relaxation frequency in the GHz range. We demonstrate that, far above the threshold current, the relaxation frequency increases with the bias current, and our simulations are in good agreement with our experimental efforts. Fitting of the relative intensity noise resonances gives access to several intrinsic parameters of the interband cascade laser under study such as differential gain, compression gain, and K-factor. This study is a clear step for understanding dynamics interplays in interband cascade laser structures, which means understanding the non-linear and modulation bandwidth limitations of such lasers.

A 5–50 GHz SiGe BiCMOS Linear Transimpedance Amplifier with 68 dBΩ Differential Gain towards Highly Integrated Quasi-Coherent Receivers

Quasi-coherent optical receivers have recently emerged targeting access networks, offering improved sensitivity and reach over direct-detection schemes at the expense of a higher receiver bandwidth. Higher levels of system integration together with sufficiently wideband front-end blocks, and in particular high-speed linear transimpedance amplifiers (TIAs), are currently demanded to reduce cost and scale up receiver data rates. In this article, we report on the design and testing of a linear TIA enabling high-speed quasi-coherent receivers. A shunt-feedback loaded common-base topology is adopted, with gain control provided by a subsequent Gilbert cell stage. The circuit was fabricated in a commercial 130 nm SiGe BiCMOS technology and has a bandpass characteristic with a 3 dB bandwidth in the range of 5–50 GHz. A differential transimpedance gain of 68 dBΩ was measured, with 896 mVpp of maximum differential output swing at the 1 dB compression point. System experiments in a quasi-coherent receiver demonstrate an optical receiver sensitivity of −30.5 dBm (BER = 1 × 10−3) at 10 Gbps, and −26 dBm (BER = 1 × 10−3) at 25 Gbps. The proposed TIA represents an enabling component towards highly integrated quasi-coherent receivers.

A miniaturized 35 GHz 65‐nm CMOS digital‐controlled differential variable gain amplifier

AbstractThis paper presents a 35 GHz differential variable gain amplifier (VGA) with 4‐bit digital‐controlled gain‐tuning using 65‐nm CMOS process. Using the proposed miniaturized differential matching inductors, a core size of the VGA is only 0.53 0.26 mm. The digital gain control mechanism is achieved using the digital version current steering topology. The measured gain control range of the VGA is from 17.4 to 9 dB at 35 GHz with 16 different linear‐in‐dB gain states. Thus, this work achieves the maximum peak gain per unit core size and maintains a much better gain control range per unit core size. The measured root mean square gain error is &lt;0.29 dB and phase error is &lt; from 34 to 36.5 GHz.

Rigorous FM-EDF design with an oversized two-layer erbium ion distribution for C-band DMG mitigation

We present a rigorous design of few-mode erbium doping fiber (FM-EDF) with an oversized two-layer erbium ion distribution at the central region with effective differential modal gain (DMG) mitigation over the C-band. The proposed erbium doping distribution allows for a similar overlapping integral value among the guided modes, leading to a signal gain equalization over the C-band. When the length of the proposed FM-EDF is 8 m under the cladding pumping power of 2.5 W, our calculated results reveal that four linearly polarized (LP)-modes can achieve an average gain per mode of 24.8 dB and a typical DMG of less than 0.64 dB over the C-band. Meanwhile, we carry out numerical simulations to explore the fabrication tolerance of the oversized two-layer erbium doping distribution with respect to the DMG, indicating stable DMG mitigation over the C-band. We believe that such new manipulation of erbium doping distribution is helpful for the multiple-dimensional multiplexing of fiber optical transmission.

High spatial-density, cladding-pumped 6-mode 7-core fiber amplifier for C-band operation.

We present a C-band 6-mode 7-core fiber amplifier in an all-fiberized cladding-pumped configuration for space division multiplexed transmission supporting a record 42 spatial channels. With optimized fiber components (e.g. passively cooled pump laser diode, pump coupler, pump stripper), high power multimode pump light is coupled to the active fiber without any noticeable thermal degradation and an average gain of 18 dB and noise figure of 5.4 dB are obtained with an average differential modal gain of 3.4 dB.

Differential gain and gain compression of an overdamped interband cascade laser

This work investigates the differential gain and gain compression factor of an interband cascade laser (ICL), through the analysis of the small-signal modulation response. The differential gain of the ICL is extracted to be 7.9 × 10−16 cm2, which is comparable to that of typical quantum well lasers. On the other hand, the gain compression factor is determined to be 5.1 × 10−15 cm3, which is two orders of magnitude higher than the latter. In addition, we demonstrate that the ICL is overdamped due to the strong gain compression effect. It is found that the K factor governed by the damping factor and the resonance frequency is as high as 31.4 ns.

Effect of thickness on the electronic structure and optical properties of quasi two-dimensional perovskite CsPbBr3 nanoplatelets

The effect of thickness of cesium lead halide perovskite CsPbBr3 nanoplatelets (NPLs) on their electronic structure and optical properties are investigated using an effective-mass envelope function theory based on the 8-band k·p model with the consideration of exciton binding energy. We first reported the CsPbBr3 nanoplatelets’ band structure and optical gain with exciton effect. As the thickness of NPLs decreases, their bandgap increases and the band mixing is more obvious which influences the transition matrix element (TME). The optical gain of CsPbBr3 nanoplatelets is calculated by taking into account of TME, Fermi factor, injected carrier density and thickness. A blue shift of peak position in optical gain can be observed as the thickness of NPLs decreases. As the injected carrier density arises, the maximum optical gain of thicker NPLs reach saturation much faster than the thinner ones. To obtain high differential gain, NPLs with less thickness are better choices. Experimental work is carried out and the results agree with our theoretical results very well.

Design of Ring-Core Few-Mode-EDFA With the Enhanced Saturation Input Signal Power and Low Differential Modal Gain

We propose a design of ring-core few-mode fiber (RC-FMF) with the erbium doping at the cladding region near the outer ring edge. After the parameter optimization of the RC-FM-EDF, the intensity overlapping difference between LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes can be minimized, leading to a DMG of 0.22 dB for the corresponding ring-core few-mode erbium-doped fiber amplifier (RC-FM-EDFA). Meanwhile, in comparison with uniform core doping design, the saturation input signal power of the RC-FM-EDFA can be enhanced from -17.7 dBm and -16 dBm to -8.5 dBm for LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> modes, respectively. Consequently, our proposed RC-FM-EDFA is characterized by both low differential modal gain (DMG) and the enhanced saturation input signal power. Those new characteristics of the RC-FM-EDFA is ideally desired for future agile networks.

Er3+/Yb3+ doped active optic Y splitter realized by diffusion waveguides with Ag+—Na+ ion exchange

We reported on the active channel waveguides, formed in novel types of silicate glasses, doped with rare-earth elements, and Zn were investigated. The silicate glass GZ4 with Er3+ and Yb3+ content was studied, and the best doping ratio was estimated about luminescent properties. The composition of the glass samples (GZ4) with the content of 0.25 mol.% Er2O3 and 5.0 mol.% Yb2O3 and 12.0 mol.% resp. 18.0 mol.% ZnO was optimized. This glass was evaluated as the most suitable material for integrated amplifiers in the 1 530–1 565 nm telecommunication band. Other samples were prepared with active channel waveguides and active planar optical power splitter Y with a splitting ratio of 1 × 2 by two-step ion-exchange Na+ ↔ Ag+. Diffusion profiles of the created samples were analyzed by the EMA microscope and compared with the near mode-field distribution measurement results. Afterward, the amplification properties of the designed structures were studied, and the differential gain from 1.2 to 1.6 dB (0.48 to 0.64 dB/cm) was achieved by pumping power 200 mW at 980 nm.

Design and simulation of high-swing fully differential telescopic Op-Amp

This article describes the process of design and simulation of a high-swing fully differential telescopic operational amplifier (Op-Amp). Due to the common gate-common source (CG and CS) cascode structure, the gain is very high. To maximize this gain, the load must also be selected such as two current sources. This circuit has the higher voltage in output than current Op-Amps in accordance with desirable characteristics. The loss of power of this operating amplifier are very low and in milliwatts. With use of a power supply of 1.8 V, it achieves a high-swing 1.2 V, a differential gain of 76.333 dB, ωuGB of 412 MHz, and &gt;50 dB CMRR. This new design through the simulations and analytically shows that the high-swing fully differential telescopic Op-Amp retains its high CMRR even at high frequencies.

Design and simulation of high-swing fully differential telescopic Op-Amp

This article describes the process of design and simulation of a high-swing fully differential telescopic Operational Amplifier (Op-Amp). Due to the Common Gate-Common Source (CG and CS) cascode structure, the gain is very high. To maximize this gain, the load must also be selected such as two current sources. This circuit has the higher voltage in output than current Op-Amps in accordance with desirable characteristics. The loss of power of this operating amplifier are very low and in milliwatts. With use of a power supply of 1.8 V, it achieves a high-swing 1.2 V, a differential gain of 76.333 dB, ω_uGB of 412 MHz, and 50 dB CMRR. This new design through the simulations and analytically shows that the high-swing fully differential telescopic Op-Amp retains its high CMRR even at high frequencies.

On‐Chip Integrated Waveguide Amplifiers on Erbium‐Doped Thin‐Film Lithium Niobate on Insulator

AbstractOn‐chip light amplification with integrated optical waveguide fabricated on erbium‐doped thin‐film lithium niobate on insulator (TFLNOI) is demonstrated using the photolithography‐assisted chemomechanical etching (PLACE) technique. A maximum internal net gain of 18 dB in the small‐signal‐gain regime is measured at the peak emission wavelength of 1530 nm for a waveguide length of 3.6 cm, indicating a differential gain per unit length of 5 dB cm−1. This work paves the way to the monolithic integration of diverse active and passive photonic components on the TFLNOI platform.