Search

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.

In this paper we are going to analyze the settling-time in single-, two- and three-stage amplifiers with the intent of deriving approximate but useful design equations that include the effects of the zeros and of the slew-rate limitations. The analysis is mainly devoted to the definition of an approach for the design of three-stage CMOS operational transconductance amplifiers from settling-time specifications. A design example is carried out to validate the proposed approach.

New five grounded immittance function simulators are proposed in this paper. The first one is a positive lossless grounded inductor simulator which employs just one inverting buffer plus-type second-generation current conveyor while the other four proposed circuits include only one non-inverting current feedback operational amplifier. The second and third ones are negative lossless grounded inductor simulators. The fourth one is a positive inductor with a series positive resistor while the last one is a negative capacitance multiplier. All of the proposed circuits except the first one consist of only grounded capacitor(s). However, all of the proposed circuits need a single passive component matching condition. A band-pass filter composed of the first proposed circuit is given as an example. Also, frequency dependent non-ideal gain effects on the performance of all the circuits are given. The results of a lot of SPICE simulations are carried out by using 0.13 µm IBM technology parameters where ± 0.75 V DC symmetrical power supply voltages are utilized. In order to demonstrate the performance of the first proposed circuit, an experimental result is given as an example. © 2018 Elsevier GmbH

In this paper, we provide a new procedure that allows to design a generic three-stage amplifier from settling-time specifications. The procedure analyze the settling-time of pure two- or three-pole amplifiers (i.e., with no zeros) and extends the results to a generic amplifier that includes one or two zeros even placed in the right-half plane. The validity of the proposed approach is demonstrated through a design example of a three-stage CMOS amplifier suitable for switched-capacitor applications.

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.

The gain-bandwidth conflict is one the most important limitations of high gain feedback amplifiers. In this tutorial paper we will discuss in a unified manner the most important approaches aimed to design amplifiers with a constant closed-loop bandwidth. Advantages and drawbacks are evidenced and new potential solutions are also formulated.

Voltage feedback is frequently used in class-D switching audio power amplifiers. This paper discusses the design and implementation of a low-cost filterless class-D, unipolar pulse-width modulation switching audio amplifier having a multi-loop voltage feedback scheme. Classical frequency-compensation techniques are used to design and stabilize the three voltage feedback loops implemented in this application. This design method proves to be a cost-effective solution for designing high-fidelity (hi-fi) audio amplifiers. The cost is reduced because no output filter is used, the required switching frequency is half of the one needed if bipolar PWM was used, and no current sensor is needed for feedback purposes. The output impedance is extremely low due to the reduction of the successive voltage loops, making the amplifier less load dependent. Simulation results show that a total harmonic distortion (THD) of 0.005% can be achieved using this topology, as well as a flat frequency response, free of phase distortion in the audio band. Experimental results show the feasibility of this control scheme, since a THD of 0.05% was achieved with a laboratory prototyped amplifier. A comparison of the performance of this audio amplifier with that of some commercial class-D audio amplifiers, reveals that our design can seriously compete with some of the ICs leading the market at a lower cost. Fil: Oliva, Alejandro Raul. University of Arkansas; Estados Unidos. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina Fil: Ang, Simon S.. University of Arkansas; Estados Unidos Fil: Vo, Thuy V.. University of Arkansas; Estados Unidos

Power modulated visible lasers are interesting for a number of applications within areas such as laser displays and medical laser treatments. In this paper, we present a system for modulating the second-harmonic light generated by single-pass frequency doubling of a distributed feedback (DFB) master oscillator power amplifier (MOPA) laser diode with separate electrical contacts for the MO and the PA. A modulation depth in excess of 97% from 0.1 Hz to 10 kHz is demonstrated. This is done by wavelength tuning of the laser diode using only a 40 mA adjustment of the current through the MO. The bandwidth of the modulation is limited by the electronics. This method has the potential to decrease the size as well as cost of modulated visible lasers. The achievable optical powers will increase as DFB MOPAs are further developed. (C) 2017 Optical Society of America

A two-stage MMIC low noise amplifier design is presented using series and shunt feedbacks to achieve simultaneously low noise, input matching and gain flatness performances across the frequency range of 4 to 12 GHz. The amplifier fits into a small die of 2×1 mm2, and achieves a flat gain of 20 dB and a minimum noise figure of 1.5 dB., 2014 16th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2014, 13 July 2014 through 16 July 2014, Victoria, BC

In this paper, a new grounded inductor simulator employing two current feedback operational amplifiers (CFOAs), three resistors and one grounded capacitor which is suitable for IC fabrication is proposed. Also, a new voltage-mode (VM) universal filter with three input and single output is given as application example of the grounded inductor simulator. The universal filter with low output impedance can be easily cascaded with other VM circuits. Both of the proposed circuits have the feature of improved low frequency performances, and can be easily constructed by two commercially available active devices such as AD844s. However, both inductor simulator and universal filter need a single passive component matching condition. Simulation and experimental test results are given to demonstrate the performance and workability of the proposed grounded inductor simulator and filter structure. © 2017 World Scientific Publishing Company.

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., This work was supported by MyCT sBIO2001-1235-C03-01d.

Delays in real systems can be of two types: i) intrinsic delays - due to the physical principles of operation of each electronic device; ii) designed delays - due to extra circuits used to add the desired delay. Previous work established the possibility of achieving bandwidth improvements using small delays inside the feedback loop of feedback amplifiers. The modeling approach followed on these contributions used only one designed delay element. The bandwidth reduction effect due to intrinsic delays was not considered on these contributions. This paper extends the concept to the general case of feedback amplifiers that incorporates delays of both types. An experimental demonstration using a simple 0.35μm BiCMOS transimpedance amplifier further confirms the proposed model. © 2006 IEEE.