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This paper describes an air cavity quad‐flat no‐leads (QFN) over‐molded plastic packaged cascode broadband GaN LNA Monolithic Microwave Integrated Circuit (MMIC) with resistive feedback fabricated with 0.25 μm GaN HEMT technology. The single stage QFN packaged GaN LNA MMIC achieves a bandwidth of 0.03–2.6 GHz with a typical gain of 11.5 dB and less than 1.5 dB noise figure. The low noise amplifier (LNA) design is based on a model of a concept transistor, the cascode transistor used in the design, that has not been fabricated previously. The concept transistor is fabricated for the first time along with the GaN LNA MMIC. The fabricated GaN LNA MMIC is housed in a 12‐lead 3 × 3 mm2 air cavity QFN over‐molded plastic package and mounted on an application board. The measurements taken with the application board represent a good convergence with the design that is based on a concept transistor model. The measurement results and 50 Ω internal matching on both ports without the need for additional matching components make this LNA attractive for many applications. [ABSTRACT FROM AUTHOR]

Source degenerative feedback is extensively applied in the low-noise amplifier design. The beneficial effects of this technique are well established in the open literature. However, the designer is often left to trial-and-error or optimization procedures to identify the adequate amount of feedback when other linear requirements, such as signal matching, come into play. This issue is even more relevant in multistage designs. In this article, we present a synthesis procedure and the relevant design chart to identify the optimum feedback inductor value on all transistors of an N-stage amplifier to obtain a perfect match at its external ports in conjunction with amplifier noise figure minimization and a specified gain requirement. It is shown that the method is applicable to arbitrary N values although it becomes more elaborate for N greater than 6. The method is deterministic as opposed to optimization or trial-and-error-based procedures. The design flow is illustrated at first through a four-stage design with ideal matching elements and subsequently validated by an monolithic microwave integrated circuit (MMIC) test vehicle designed and realized in the WIN foundry’s Gallium Arsenide PIH1-10 process. The measured performance of the test vehicle is NF = 1.9 dB, 26 dB gain, typical I/O return loss of 15 dB in the 26.5–29.5-GHz bandwidth, and practically ideal behavior at the design frequency of 28 GHz. [ABSTRACT FROM AUTHOR]

A positive feedback gain‐enhanced technique for power amplifiers has been introduced in this Letter. With the proposed circuit design method for optimal inductive feedback, a 180 GHz high‐gain single‐stage cascode power amplifier in a 130 nm SiGe process is implemented. The measurement results show a power gain of 10 dB and 20 GHz bandwidth with 110 mW dc power are achieved, and 6.5 dBm of output power referred to P1dB and 3.5% collector efficiency are attained. The chip area of the power amplifier is only 0.50 × 0.48 mm2. [ABSTRACT FROM AUTHOR]

To guarantee that all mobile users in a cell can watch video with acceptable quality, conventional multicast IPTV services use the most robust modulation and coding scheme (MCS) for video transmission, resulting in worse spectral efficiency. To enhance the spectral efficiency, the adaptive multicast IPTV using the adaptive MCS based on signal-to-noise ratios (SNRs) or channel quality indicators (CQIs) was proposed in the literature. However, the CQI feedback messages induced by the adaptive multicast IPTV incur additional signaling overhead. Thus, a novel CQI feedback scheme was proposed in this paper to effectively decrease the amount of CQI feedback messages while preserving the system performance. Additionally, the CQI feedback rates of various CQI feedback schemes were theoretically analyzed based on the multi-dimensional Markovian model. Numerical results show that the proposed CQI feedback mechanism significantly reduces the CQI feedback rate without sacrificing the system performance and outperforms other existing CQI feedback schemes. Moreover, the analytical results almost coincide with simulation results, demonstrating that the theoretic analyses are accurate. [ABSTRACT FROM AUTHOR]

The performance of devices based on micro- and nanomechanical oscillators depends critically on the quality factor (Q). The quality factor can be externally increased about two orders of magnitude by coherent amplification of the oscillation at resonance with a fast feedback amplifier. Here, theory and experiments performed with microcantilevers are presented to study the oscillation noise under external Q enhancement and how it differs from the noise when the Q is naturally enhanced by decreasing the mechanical energy loss. The application of the feedback amplifier produces a significant increase of the thermal noise and the noise that arises from the cantilever-displacement sensor. The main consequence is that the signal-to-noise ratio (S/N) remains constant and independent of the Q enhancement when measuring the amplitude and phase of the oscillation in the slope detection technique. This behavior is opposite to the enhancement of the S/N when the Q naturally increases, which is proportional to Q1/2, ignoring instrumental sources of noise. More important, by taking into account the maximum driving force provided by the actuator, it is concluded that external Q enhancement does not enhance the sensitivity of devices based on micro- and nanomechanical oscillators, using the slope detection technique. The lack of sensitivity enhancement is attributed to the fact that thermal forces are not altered by the increase of the quality factor via the fast feedback amplifier. Finally, it is proposed to use the fast feedback amplifier in a different measurement mode to obtain high sensitivity. This consists in the self-excitation of the cantilever without application of a reference driving force, and the measurement of the frequency of the oscillation. Self-excitation of the cantilever produces amplification of the noise and its squeezing around the resonant frequency, hence the oscillation resembles Brownian motion of the cantilever with a superior quality factor. [ABSTRACT FROM AUTHOR]

The small amplitude thermal vibrations of the microcantilever of an atomic force microscope can be enhanced via a delayed feedback system. This is verified experimentally for a triangular cantilever, and modeled theoretically as a boundary value problem resulting in a second order functional differential equation for the temporal behavior of the cantilever. The eigenvalues of the resulting delay differential equation describing the transverse vibrations of the cantilever are calculated and analyzed. These values are compared with the corresponding resonant frequencies predicted by a point mass model and with the experimentally observed values. [ABSTRACT FROM AUTHOR]

Today’s data center operators deploy network policies in both physical (e.g., middleboxes, switches) and virtualized (e.g., virtual machines on general purpose servers) network function boxes (NFBs), which reside in different points of the network, to exploit their efficiency and agility respectively. Nevertheless, such heterogeneity has resulted in a great number of independent network nodes that can dynamically generate and implement inconsistent and conflicting network policies, making correct policy implementation a difficult problem to solve. Since these nodes have varying capabilities, services running atop are also faced with profound performance unpredictability. In this paper, we propose a Heterogeneous netwOrk Policy Enforcement (HOPE) scheme to overcome these challenges. HOPE guarantees that network functions (NFs) that implement a policy chain are optimally placed onto heterogeneous NFBs such that the network cost of the policy is minimized. We first experimentally demonstrate that the processing capacity of NFBs is the dominant performance factor. This observation is then used to formulate the Heterogeneous Network Policy Placement problem, which is shown to be NP-Hard. To solve the problem efficiently, an online algorithm is proposed. Our experimental results demonstrate that HOPE achieves the same optimality as Branch-and-bound optimization but is 3 orders of magnitude more efficient. [ABSTRACT FROM AUTHOR]

This paper proposes a novel semi-blind uplink interference suppression scheme for multicell multiuser massive multiple-input multiple-output (MIMO) systems. The inter-cell interference (ICI) becomes intenser when a number of users are spatially multiplexed via massive MIMO. Here arises a pilot contamination problem due to the limitation of orthogonal sequence set and thus inter-user interference (IUI) also remains unsuppressed. Our proposal employs a constant modulus algorithm (CMA) known as a blind interference suppression scheme and exploits channel state information (CSI)-aided minimum mean square error (MMSE) postcoding weight as an initial weight of CMA. Although MMSE weight cannot suppress ICI and IUI due to the pilot contamination, it can help subsequent CMA to capture the desired signals which is required for CMA to effectively work. Since CMA can fully exploit degree of freedom of massive arrays by using uncorrelated data signal part, derived weight successfully suppresses ICI/IUI while resolving the pilot contamination problem. A decision feedback channel estimation (DFCE) is then introduced to further improve CSI estimation accuracy and subsequent interference suppression performance. A series of signal processing, MMSE–CMA–DFCE, can be iteratively performed. The computer simulation reveals that our proposal can improve outage probability and it satisfies below the fifth percentile of cumulative distribution with saved symbol amount. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we introduce a simple and well‐defined approach for the design of fast settling amplifiers suitable for switched‐capacitor circuits and characterized by low capacitive loads, in the order of few pico‐farad. In the specific, the design is based on a new Bessel‐like compensation that sets the phase of the closed‐loop amplifier to be linearly related to the frequency, thus emulating the behavior of an ideal delay, like in a Bessel filter. The proposed Bessel‐like approach is validated through the design and the simulation of two 3‐stage amplifiers in a 65‐nm CMOS process. [ABSTRACT FROM AUTHOR]

With M sampling operational amplifiers (op‐amps) in negative feedback, the fast readout zero potential circuit (FRZPC) can simultaneously access M elements in the M × N resistive sensor array with the shared row–column fashion but it suffered from the crosstalk problem caused by the switch‐on resistance of the column multiplexers, the non‐scanned elements and the size of the array. For suppressing the crosstalk problem, the authors[AQ ID=Q2] proposed an improved FRZPC, called IFRZPC, by introducing one more op‐amp in negative feedback to sample the current in the ground to the array direction. Then, in the FRZPC and the IFRZPC, the effects of different parameters of the resistive sensor array and the readout circuit on the measurement accuracy of the elements being tested were simulated using National Instrument Multisim. Simulations and comparative experiments were performed and demonstrated that IFRZPC, though requiring M + 1 op‐amps, M + 1 resistors, and M + 1 sampling channels, could simultaneously access M elements being tested on the same column in the M × N resistive sensor array with a better accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a novel decorrelation-based concurrent digital predistortion (DPD) solution is proposed for dual-band transmitters (TXs) employing a single wideband power amplifier (PA), and utilizing only a single feedback receiver path. The proposed decorrelation-based parameter learning solution is both flexible and simple, and operates in a closed-loop manner, opposed to the widely applied indirect learning architecture. The proposed decorrelation-based learning and DPD processing can also be effectively applied to more ordinary single carrier/band transmissions, as well as generalized to more than two transmit bands. Through a comprehensive analysis covering both the DPD parameter learning and the main path processing, it is shown that the complexity of the proposed concurrent DPD is substantially lower compared with the other state-of-the-art concurrent DPD methods. Extensive set of simulation and RF measurement results are also presented, using base-station PAs as well as a commercial LTE-Advanced mobile PA, to evaluate and validate the effectiveness of the proposed DPD solution in various real world scenarios, incorporating both single-band and dual-band TX cases. The simulation and RF measurement results demonstrate excellent linearization performance of the proposed concurrent DPD, even outperforming current state-of-the-art methods, despite the significantly lower complexity. [ABSTRACT FROM AUTHOR]

This paper presents a new feedback model that focuses on the synthesis rather than the analysis of feedback amplifiers. First, a single-loop synthesis-oriented feedback model is developed that enables the full synthesis of such amplifiers in a hierarchical and systematic way. This model is subsequently extended to a double-loop synthesis model, so that also feedback amplifiers with a characteristic input or output impedance-employing two feedback loops-can be synthesized through the same systematic approach. That these new models are suitable for synthesis lies in the fact that they map directly to the circuit level, such that the intended, asymptotic behavior as well as the various individual contributors to the deviation from this intended behavior, like finite loop gain, non-ideal input and output impedances of the forward gain block, direct feed-through and attenuations outside the feedback loop(s), are clearly distinguished and can be assigned to the responsible sections of the network. For this purpose, the double-loop synthesis model makes the transfers of the two feedback networks explicitly visible, so that it gives immediate insight in how to design these networks to get the required signal transfer and characteristic impedance. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Based upon the experimental results of the two CFOA-based fully-uncoupled sinusoidal oscillators proposed earlier by Bhaskar-Gupta-Senani-Singh, recently Abuelma’atti and Khalifa issued a caution that the classification of this class of oscillators providing independent control of condition of oscillation (CO) and frequency of oscillation (FO) through separate elements, as fully-uncoupled , does not appear to be correct. In this communication, we present the results of a recheck of the experimental data of Abuelma’atti and Khalifa and show that their experimental results are not repeatable and in most of the cases , the oscillations do not even exist and hence, the measurement data as given by them is misleading. Furthermore, it is shown that the measured oscillation frequencies, as shown by Abuelma’atti and Khalifa in four tables, do not tally with those calculated from their own formula as well as the experimental results taken by us. This communication thus, refutes the claims made in the quoted paper of Abuelma’atti and Khalifa published in this journal earlier. [ABSTRACT FROM AUTHOR]

We address the global stabilization of linear time-invariant (LTI) systems when the magnitude of the control input and its successive time derivatives, up to an arbitrary order p ∈ N, are bounded by prescribed values. We propose a static state feedback that solves this problem for any admissible LTI systems, namely, for stabilizable systems whose internal dynamics has no eigenvalue with a positive real part. This generalizes previous work done for single-input chains of integrators and rotating dynamics. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new approach for the robust design of complementary metal-oxide-semiconductor amplifiers based on settling-time specifications. The approach is based on the definition of the separation factors and on the analysis of their role in the settling time. We define a design strategy for being certain that an OTA satisfies the settling-time constraint under any statistical variation of process or design parameters. The proposed strategy is applied to the transistor level design of a two-stage amplifier and a three-stage one. Simulation results, in good agreement with theory, confirm the validity of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A linear voltage controlled quadrature oscillator implemented from a first-order electronically tunable all-pass filter (ETAF) is presented. The active element is commercially available current feedback amplifier (AD844) in conjunction with the relatively new Multiplication Mode Current Conveyor (MMCC) device. Electronic tunability is obtained by the control node voltage (V) of the MMCC. Effects of the device nonidealities, namely, the parasitic capacitors and the roll-off poles of the port-transfer ratios of the device, are shown to be negligible, even though the usable high-frequency ranges are constrained by these imperfections. Subsequently the filter is looped with an electronically tunable integrator (ETI) to implement the quadrature oscillator (QO). Experimental responses on the voltage tunable phase of the filter and the linear-tuning law of the quadrature oscillator up to 9.9 MHz at low THD are verified by simulation and hardware tests. [ABSTRACT FROM AUTHOR]

In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1 THz and 0.6 THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45 dB. [ABSTRACT FROM AUTHOR]

The operating cost of islanded microgrids (\rm\mu G s) can be minimized by performing an optimal power sharing among the distributed generators ( \rmDGs). In this study, a plug-and-play optimization scheme (PPOS) for developing nonlinear droop relations is proposed to achieve an optimal power sharing among \rmDGs in islanded \rm\mu Gs. The PPOS constructs optimal nonlinear relations for each \rmDG, which are used as nonlinear droop curves that adjusts the output power of the \rmDG s subsequent to any load variation to minimize the \rm\mu G operating cost effectively. The construction of nonlinear droop relations in the PPOS is performed individually for each DG by optimizing each one against hypothetical \rmDGs. This approach provides an indirect optimization among different \mathbfDG s in the \mu G network and ensures an operating cost minimization irrespective of the {\rm{\mu G\;}} topology. An islanded \rm\mu G topology has been developed and simulated in MATLAB/Simulink environment to verify the effectiveness of the proposed method and the performance of the nonlinear droop control. An experimental study has also been conducted on a {\rm{\mu G\;}}$ test bed to prove the effectiveness of the nonlinear power sharing and to verify the performance of the nonlinear droop control in the {\rm{\mu G\;}} operating cost minimization. [ABSTRACT FROM AUTHOR]

Lossless Feedback Delay Networks (FDNs) are commonly used as a design prototype for artificial reverberation algorithms. The lossless property is dependent on the feedback matrix, which connects the output of a set of delays to their inputs, and the lengths of the delays. Both, unitary and triangular feedback matrices are known to constitute lossless FDNs, however, the most general class of lossless feedback matrices has not been identified. In this contribution, it is shown that the FDN is lossless for any set of delays, if all irreducible components of the feedback matrix are diagonally similar to a unitary matrix. The necessity of the generalized class of feedback matrices is demonstrated by examples of FDN designs proposed in literature. [ABSTRACT FROM PUBLISHER]

We propose a new design, Physical Unclonable Function (PUF) scheme, for the Internet of Things (IoT), which has been suffering from multiple-level security threats. As more and more objects interconnect on IoT networks, the identity of each thing is very important. To authenticate each object, we design an impedance mismatch PUF, which exploits random physical factors of the transmission line to generate a security unique private key. The characteristic impedance of the transmission line and signal transmission theory of the printed circuit board (PCB) are also analyzed in detail. To improve the reliability, current feedback amplifier (CFA) method is applied on the PUF. Finally, the proposed scheme is implemented and tested. The measure results show that impedance mismatch PUF provides better unpredictability and randomness. [ABSTRACT FROM AUTHOR]

This paper presents four new topologies for emulating floating immittance functions. Each circuit uses two or three current-feedback operational-amplifiers (CFOAs) and three passive elements. The proposed topologies can emulate positive/negative lossless and lossy floating inductances, and positive/negative capacitance, resistance and inductance multipliers in addition to floating frequency-dependent positive and negative resistances. The functionality of the proposed circuits is verified using the Advanced Design System software and the AD844 CFOA. The simulation results are in excellent agreement with the theoretical calculations. [ABSTRACT FROM PUBLISHER]

A new concept of a Charge Sensitive Amplifier without a high-value resistor in the feedback loop is presented. Basic spectroscopic parameters of the amplifier coupled to a coaxial High Purity Germanium detector (HPGe) are discussed. The amplifier signal input is realized with an n-channel J-FET transistor. The feedback capacitor is discharged continuously by the second, forward biased n-channel J-FET, driven by an RC low–pass filter. Both the analog—with a standard spectroscopy amplifier and a multi-channel analyzer—and the digital—by applying a Flash Analog to Digital Converter—signal readouts were tested. The achieved resolution in the analog and the digital readouts was 0.17% and 0.21%, respectively, at the Full Width at Half Maximum of the registered 60 Co 1332.5 keV gamma line. [ABSTRACT FROM AUTHOR]

In this paper, a new approach is presented to calculate the stability margin of the discrete systems. It is based on the algorithm for reduced conservatism of eigenvalues and the Gerschgorin circle theorem. The necessary and sufficient condition for conservatism of eigenvalues of matrix is stated and proved mathematically. Moreover, the proposed approach is illustrated with an example and it is compared with the other existing methods. [ABSTRACT FROM AUTHOR]

This paper shows the design of an active patch antenna. First, an analysis of the electric field inside the patch is performed to determine the compatibility of the modes of the patch with the desired feeding. The desired feeding is as a serial two-port resonator, so the suitable mode is the “Mode 1”. Then a linear analysis of the active antenna is performed. In this particular example, it is possible to use the classic Loop Gain Method, but its use is not guaranteed. So, the proposed NDF Method is used because it is independent of the oscillator topology and it is valid without any restriction or proviso. Then a Harmonic Balance analysis is performed and the results are compared with the measurements of a prototype. [ABSTRACT FROM AUTHOR]

ABSTRACT Firstly, a compact current feedback amplifier-based negative impedance converter (CFA-based NIC) was designed and its equivalent circuit was proposed. Secondly, to obtain a stable negative inductor, a stabilization network was developed and combined with the CFA-based NIC. Meanwhile, the stability of the combined circuit was analyzed in detail in the time domain by the method of Routh-Hurwitz criterion (R-H criterion). Finally, the prototype of the designed CFA-based NIC with stabilization network was fabricated. The measurement results had a good agreement with simulated results. The measurement results showed the negative inductivity of the input impedance over a wideband from 50 to 500 MHz. Especially, the equivalent inductor of the present circuit is −3.4 nH ± 10% from 200 to 500 MHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1723-1728, 2016 [ABSTRACT FROM AUTHOR]

The design of fractional-order filters using Current Feedback Operational Amplifiers as active elements, is presented in this paper. The first step of the procedure is the approximation of the fractional-order transfer function by an appropriate integer-order function and the derivation of the corresponding Functional Block Diagram. As a second step, the implementation of the derived Functional Block Diagram is performed through the utilization of integration and summation blocks constructed from Current Feedback Operational Amplifiers. As a design example, a 1+a order (0

A dual-loop feedback broadband low-noise amplifier (LNA) employing second-order inter-modulation distortion (IMD2) cancellation is implemented in an 0.18- \mu \text m silicon-on-insulator (SOI) CMOS technology. The dual-loop feedback configuration stabilizes an input return loss ( S 11 ) of the LNA at the VHF low band around 50 MHz with small dc blocking capacitors. In order to achieve a second-order output-referred intercept point (OIP2) of greater than +50 dBm with reasonably low power consumption, all of the building blocks of the proposed LNA are designed to have a complementary configuration while the body-bias control technique is applied to the inverter-based resistive feedback amplifier. In addition, the peaking inductor is placed inside the feedback loop at the gate of the input transistor to enhance the bandwidth of the LNA. The designed LNA achieves a measured power gain ( S 21 ) of 10.1 dB, a noise figure (NF) of less than 4 dB, and an input return loss ( S 11 ) of greater than 10 dB over frequencies ranging from 50 MHz to 3 GHz. The measurements show a third-order output-referred intercept point (OIP3) of +17.8 dBm and an OIP2 of +53 dBm at 1 GHz. [ABSTRACT FROM PUBLISHER]

The paper presents an analysis of problems associated with the area and power reduction of readout circuits used in multichannel neurobiology experiments, in relation to noise minimization. The noise limits of a single channel considered as a function of the silicon occupation and power consumption are analyzed for an amplifier working with capacitive feedback. The paper also presents an efficient method of noise minimization in multichannel recording systems used in neurobiology experiments, when the power budget and silicon area per single recording channel are strictly limited. The proposed idea was verified in an eight-channel prototype integrated circuit fabricated in CMOS 180 nm process. The prototype IC measurements show that with the use of the proposed method, one can decrease the recording channels’ noise two times with the existing dedicated power and area budget. [ABSTRACT FROM AUTHOR]

In this paper, two proposed bandwidth (BW) extension techniques are discussed and analytically analyzed. The capabilities of the proposed feedback techniques are demonstrated with two design examples of different circuitry, supported by simulation and measurement results. The first design example is a broadband low-power active balun, employing one of the presented feedback techniques. It is capable of operating with a gain of 2.2 dB and BW of more than 70 GHz. The amplitude imbalance is less than 2.4 dB, while the phase imbalance is below 7^\circ up to 60 GHz and 14^\circ up to 70 GHz, consuming a low-power of 29.7 mW. The second design example is a differential three-stage amplifier, incorporating the two techniques, where their combined performance achieves a gain of 54 dB and a 3-dB BW of 25 GHz, resulting in a gain-BW product (GBP) of 12.5 THz, with a power consumption of 180 mW from a 3.3-V supply. The chips are fabricated in a 0.35-\mum SiGe:C bipolar technology with a f_t/ f\max of 200/250 GHz. [ABSTRACT FROM PUBLISHER]

A low‐noise, wide‐bandwidth DNA readout instrument for nanopore applications is presented. Owing to hardware simplicity and reliability, a resistive‐feedback transimpedance amplifier (rf‐TIA) is adopted as the headstage for the readout instrument. However, to achieve a high gain and low input noise, its high feedback resistance induces a high parasitic capacitance, thus significantly limiting the 3 dB bandwidth. To drastically reduce the parasitic capacitance and widen the bandwidth, a novel rf‐TIA architecture is fabricated that utilises a split‐resistor technique for the high feedback resistor. This is demonstrated in a benchtop test employing an α‐haemolysin nanopore. [ABSTRACT FROM AUTHOR]

A class AB differential difference amplifier for continuous‐time common‐mode feedback (CMFB) is presented. It employs local CMFB to improve gain‐bandwidth product and dynamic performance of the CMFB loop, without increasing static power consumption or supply voltage requirements. Measurement results for a 0.5 μm CMOS test chip prototype validate the proposal. [ABSTRACT FROM AUTHOR]

The use of positive feedback as a solution to intrinsic gain degradation in scaled CMOS technologies, such as 65 nm and below, is discussed in detail. Criteria for increasing gain while keeping the system stable are derived using a positive feedback amplifier model. These criteria are shown to provide significant gain enhancement in silicon. This work extends the previously reported DC gain analysis to include evaluation of additional effects of positive feedback as well an investigation of the frequency behavior using S-parameter measurements in silicon. These S-parameter measurements of fully differential positive feedback amplifiers designed in TSMC's 65 nm technology show gain enhancements of up to 26.7 dB at frequencies up to 8.5 GHz. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The influence of external circuit designs on ASET shapes in a high speed current feedback amplifier (CFA) (AD844) is investigated by means of the pulsed laser single event effect (PLSEE) simulation technique. Changes of the feedback resistors modify circuit’s electrical parameters such as closed-loop gain and bandwidth, affecting amplifier stability and so ASET shapes. Qualitative explanations based on general electronic rules and feedback theories enable the understanding of a CFA operation establishing a correlation between the evolution of external feedback resistor values and ASET parameters. TID effects on the ASET sensitivity in AD844 CFA are also investigated in this work highlighting different behaviors according to the impacted bipolar transistor in the integrated circuit. [ABSTRACT FROM PUBLISHER]

ABSTRACT This paper introduces novel four-phase oscillator employing two Dual-Output Controlled Gain Current Follower Buffered Amplifiers (DO-CG-CFBAs), single Current Amplifier, three resistors, and two grounded capacitors suitable for differential quadrature signal production (floating outputs). To control the frequency of oscillation (FO) and condition of oscillation (CO), only the current gain adjustment of active elements is used. The circuit was designed by well-known state variable approach. The oscillator employs three active elements for linear control of FO and to adjust CO and provides low-impedance voltage outputs. Furthermore, two straightforward ways of automatic amplitude gain control were used and compared. Active elements with very good performance are implemented to fulfill required features. Suitable CMOS implementation of introduced DO-CG-CFBA was shown. Important characteristics of the designed oscillator were verified experimentally and by PSpice simulations to confirm theoretical and expected presumptions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a bandwidth enhancement technique for broadband Darlington amplifiers. A detailed analysis of the high-frequency performance of the Darlington amplifier and the effect of bandwidth enhancement is provided. A design procedure is also given for broadband feedback Darlington amplifiers with bandwidth enhancement and gain flattening. A single- and a three-stage feedback amplifier with the proposed improvements are designed and implemented in a 0.25-\mu\ m AlGaAs–InGaAs pHEMT technology. The single-stage amplifier provides \ 6\pm \ 0.4~\ dB of small-signal gain in the frequency band of 1–30 GHz. The three-stage amplifier features \ 17.8\pm \ 0.8~\ dB of small-signal gain in the frequency band of 2–29 GHz. It provides a gain-bandwidth product of 217 GHz, which is 3.3 times larger than the unity gain frequency (f T) of the process. [ABSTRACT FROM AUTHOR]

This study investigates the closed-loop performance of the basic current feedback operational amplifier (CFOA), with particular emphasis on its dynamic response. It also focuses on the design, performance and advantages of the CFOA in its ability to provide a substantially constant closed-loop bandwidth for closed-loop voltage gain. Furthermore, an improved CFOA with wide bandwidth and common-mode-rejection ratio (CMRR) performance is also presented. The design presented in this article uses a bootstrapping technique with Quasi-Darlington in the input stage to reduce the influence of the Early effect which results in improved performance. Another advantage of this design is that the inverting input impedance is reduced significantly, which leads to further improvement in bandwidth and CMRR. [ABSTRACT FROM PUBLISHER]

This paper deals with an extension of the Rosenstark's linear model of an amplifier to a nonlinear one for the purpose of performing nonlinear distortion analysis. Contrary to an approach using phasors, our method uses the Volterra series. Relying upon the linear model mentioned above, we define first a set of the so-called amplifier's constitutive equations in an operator form. Then, we expand operators using the Volterra series truncated to the first three components. This leads to getting two representations in the time domain, called in-network and inputoutput type descriptions of an amplifier. Afterwards, both of these representations are transferred into the multi-frequency domains. Their usefulness in calculations of any nonlinear distortion measure as, for example, harmonic, intermodulation, and/or cross-modulation distortion is demonstrated. Moreover, we show that they allow a simple calculation of the so-called nonlinear transfer functions in any topology as, for example, of cascade and feedback structures and their combinations occurring in single-, two-, and three-stage amplifiers. Examples of such calculations are given. Finally in this paper, we comment on usage of such notions as nonlinear signals, intermodulation nonlinearity, and on identification of transfer function poles and zeros lying on the frequency axis with related real-valued frequencies. [ABSTRACT FROM AUTHOR]

In this paper, a novel grid multiscroll chaotic electronic oscillator with simple circuit design is proposed. The proposed grid multiscroll chaotic circuit only needs two current feedback operational amplifiers (CFOAs) as current integrators, passive RC, and nonlinear elements in the form of current stair nonlinear function series (SNFS) realized with CFOAs. Compared with existing grid multiscroll circuits such as Chua's circuit and Jerk circuit, etc., its component count is reduced. Mathematical models of the proposed generators are derived. Theoretical analysis and numerical simulations of the derived models are included. Moreover, the experimental results are verified that the proposed simpler chaotic electronic oscillator can generate grid multiscroll chaotic attractors with higher frequency. [ABSTRACT FROM AUTHOR]

Constant input and output mismatch circles in the output load plane are introduced as the basis for low-noise amplifier design methodology. Optimum tradeoff between input and output matching levels results as the application of a design chart providing, at the same time, the corresponding stage transducer gain. The role of degenerative series feedback is studied and systematically embedded in the design procedure, thus providing a direct way to evaluate its optimum level. [ABSTRACT FROM AUTHOR]

In this work, the package influence on a feedback low-noise amplifier has been studied.The electromagnetic simulator of ADS was used to obtain the QFN16 package model and the bonding model. The influence of the package and the pad on the supply node was negligible when it was studied separately. However, the circuit performance is reduced when the inductance introduced by the bonding of the supply node is combined with the parasitic capacities associated to the pad with electrostatic discharge protection. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1435-1440, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27601 [ABSTRACT FROM AUTHOR]

ABSTRACT We present an adaptive frequency compensation technique providing maximum bandwidth closed-loop amplifiers. The approach exploits an auxiliary variable gain amplifier to implement an electrically tunable compensation capacitor proportional to the feedback factor. In this manner, the closed-loop bandwidth is kept ideally constant irrespective of the closed-loop gain. The proposed method can be applied to any amplifier adopting dominant-pole compensation. As an example, we designed a CMOS amplifier providing 66-dB direct current gain and 310-MHz gain-bandwidth product. For closed-loop gains ranging from 1 to 10, the closed-loop bandwidth was found never lower than 401 MHz (noinverting configuration) and 229 MHz (inverting configuration). A similar amplifier with equal gain-bandwidth product, but adopting the traditional fixed compensation approach, would exhibit a closed-loop bandwidth reduced to 33 MHz (noninverting) and 30 MHz (inverting) when the gain magnitude is set to 10. The enhanced frequency performance is obtained with a 48% increase in current consumption, whereas the other main operational amplifier performance parameters remain almost unchanged compared with the standard solution. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper we describe the design of a low noise amplifier (LNA) using two feedback loops, one with a transformer, and the other with a resistor. We determine first the double loop feedback (DLF) topologies that are suitable for LNA design. One of these is analyzed in detail, first assuming an ideal amplifying block, and then with a nonideal block (to determine the gain required for the amplifying block to be considered as ideal). Simulation results show that it is possible to obtain wideband DLF LNAs with very low noise figure. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a current-steering approach to implement a fast transient response low-dropout regulator (LDO) based on a current feedback amplifier (CFA) topology. The circuit does not require any internal compensation capacitor, being stable for a wide range of output load currents [0–100mA] and a 1μF output capacitor. The CFA consists of an open-loop voltage follower with output local current–current feedback based on a level-shifted flipped voltage follower (LSFVF) which is instrumental to achieve high regulation and fast transient response. The inverting output buffer stage of the CFA together with current-mirror-based driving of the power pass transistor results in high PSRR. Post-layout simulation results for a 0.35μm CMOS process design reveal that the proposed LDO requires 59μA quiescent current at no-load condition and at full-load condition has a current efficiency of 99.8%. For a 1μF output capacitor, the maximum output voltage variation to a 0–100mA load transient with rise and fall times of 10 and 100ns is only 3mV, and the PSRR is smaller than −56dB over the entire load current range. [Copyright &y& Elsevier]

This paper proposes a multistage transformer-feedback-based design approach for a high fractional-bandwidth (fBW) IF stage in a 60-GHz heterodyne receiver. An in-depth analysis of source-to-gate transformer-feedback amplifiers, including the design of the matching network, is presented. Analytic expressions for the input resistance, quality factor, and noise figure (NF) as a function of the transformer turns-ratio (n) and magnetic coupling factor (k) are derived. To validate the proposed analysis, a wideband IF amplifier and mixer were designed in a 40-nm CMOS process. From measured results, this device achieves a 16% -3-dB fBW, a peak power gain of 27.6 dB, an NF of 5.3 dB while consuming 28.8 mW from a 0.9-V supply. [ABSTRACT FROM AUTHOR]

We successfully fabricated a large-area flexible strain-sensing system based on a 2-D array of organic self-bias-feedback amplifier with a signal gain of 400. The amplifier system consists of three layers: a self-assembled monolayer (SAM) capacitor matrix, a 2-D array of organic pseudo-CMOS inverters with a floating-gate structure using SAM gate dielectric, and an active matrix of organic thin-film transistors. The amplifier sheet comprises 8 \times 8 amplifier cells, with an effective size of \7 \times \7\ \cm^2. The organic transistors exhibit a mobility of 1.7 \cm^2/\V\cdot \s in the saturation regime at an operation voltage of 2 V. A strain sensor is made of a polymeric piezoelectric [polyvinylidene difluoride (PVDF)] sheet. When a cell of the PVDF sheet is touched (that is, when mechanical pressure is applied), a small signal is generated by intermolecular polarization in the PVDF. These signals are amplified by the organic amplifier circuits from 10 to 150 mV. [ABSTRACT FROM AUTHOR]