The need for high performance circuits in systems with low-voltage and low-power requirements has exponentially increased during the few last years due to the sophistication and miniaturization of electronic components. Most of these circuits are required to have a very good efficiency behavior in order to extend the battery life of the device. This dissertation addresses two important topics concerning very high efficiency circuits with very high performance specifications. The first topic is the design and implementation of class D audio power amplifiers, keeping their inherent high efficiency characteristic while improving their linearity performance, reducing their quiescent power consumption, and minimizing the silicon area. The second topic is the design and implementation of switching voltage regulators and their controllers, to provide a low-cost, compact, high efficient and reliable power conversion for integrated circuits. The first part of this dissertation includes a short, although deep, analysis on class D amplifiers, their history, principles of operation, architectures, performance metrics, practical design considerations, and their present and future market distribution. Moreover, the harmonic distortion of open-loop class D amplifiers based on pulse-width modulation (PWM) is analyzed by applying the duty cycle variation technique for the most popular carrier waveforms giving an easy and practical analytic method to evaluate the class D amplifier distortion and determine its specifications for a given linearity requirement. Additionally, three class D amplifiers, with an architecture based on sliding mode control, are proposed, designed, fabricated and tested. The amplifiers make use of a hysteretic controller to avoid the need of complex overhead circuitry typically needed in other architectures to compensate non-idealities of practical implementations. The design of the amplifiers based on this technique is compact, small, reliable, and provides a performance comparable to the state-of-the-art class D amplifiers, but consumes only one tenth of quiescent power. This characteristic gives to the proposed amplifiers an advantage for applications with minimal power consumption and very high performance requirements. The second part of this dissertation presents the design, implementation, and testing of switching voltage regulators. It starts with a description and brief analysis on the power converters architectures. It outlines the advantages and drawbacks of the main topologies, discusses practical design considerations, and compares their current and future market distribution. Then, two different buck converters are proposed to overcome the most critical issue in switching voltage regulators: to provide a stable voltage supply for electronic devices, with good regulation voltage, high efficiency performance, and, most important, a minimum number of components. The first buck converter, which has been designed, fabricated and tested, is an integrated dual-output voltage regulator based on sliding mode control that provides a power efficiency comparable to the conventional solutions, but potentially saves silicon area and input filter components. The design is based on the idea of stacking traditional buck converters to provide multiple output voltages with the minimum number of switches. Finally, a fully integrated buck converter based on sliding mode control is proposed. The architecture integrates the external passive components to deliver a complete monolithic solution with minimal silicon area. The buck converter employs a poly-phase structure to minimize the output current ripple and a hysteretic controller to avoid the generation of an additional high frequency carrier waveform needed in conventional solutions. The simulated results are comparable to the state-of-the-art works even with no additional post-fabrication process to improve the converter performance.

Innovation in wireless communication has resulted in accelerating demand for smartphones using multiple communications protocols such as WiFi, Bluetooth and the many cellular standards deployed around the world. The variety of frequency, bandwidth and power requirements associated with each standard typically calls for the implementation of separate radio frequency (RF) front end hardware for each standard. This is a less-than-ideal solution in terms of cost and device area. Software-defined radio (SDR) promises to solve this problem by allowing the RF hardware to be digitally reconfigurable to adapt to any wireless standard. The application of machine learning and cognition algorithms to SDR will enable cognitive radios and cognitive wireless networks, which will be able to intelligently adapt to user needs and surrounding radio spectrum conditions. The challenge of fully reconfigurable transceivers is in implementing digitally-controlled RF circuits which have comparable performance to their fixed-frequency counterparts. Switching-mode power amplifiers (SMPA) are likely to be an important part of fully reconfigurable transmitters since their switching operation provides inherent compatibility with digital circuits, with the added benefit of very high efficiency. As a step to understanding the RF requirements of high efficiency and switching PAs, an inverse class F PA in push-pull configuration is implemented. This configuration is chosen for its similarity to the current mode class D (CMCD) topology. The fabricated PA achieves a peak drain efficiency of over 75% with 42.7 dBm (18.6 W) output power at 2.46 GHz. Since SMPAs cannot directly provide the linearity required by current and future wireless communications standards, amplitude information must be encoded into the RF signal in a different way. Given the superior time resolution of digital integrated circuit (IC) technology, a logical solution is to encode this information into the timing of the signal. The two most common techniques for doing so are pulse width modulation and delta-sigma modulation. However, the design of delta-sigma modulators requires simulation as part of the design process due to the lack of closed-form relationships between modulator parameters (such as resolution and oversampling) and performance figures (such as coding efficiency and signal quality). In particular, the coding efficiency is often ignored although it is an important part of ensuring transmitter efficiency with respect to the desired signal. A study of these relationships is carried out to observe the tradeoffs between them. It is found that increasing the speed or complexity of a DS modulated system does not necessarily translate to performance benefits as one might expect. These observations can have a strong impact on design choices at the system level.

This master thesis is about current operational amplifiers and mainly about their internal structures and possible modifications of these structures. The Current operational amplifier consists of several elementary blocks and these blocks are shortly described and used in internal structures of proposed operational amplifiers. Basic elementary blocks of the current operational amplifier are current mirror, diferentional amplifier, current source, transimpedation amplifier and additional elements of a circuit. In this thesis, several elementary structures of the operational amplifiers are introduced. Each amplifier passed through the analysis of the circuit in software MicroCap 9.0. In this software is done the simple DC analysis of the internal structure of the current operational amplifier in connection with a feedback. The solution was focused on bipolar and unipolar technology for each connection. I deal with a method of feedback connection to the operational amplifier and explore real characteristic of the appropriate amplifier in the designed feedback. In principle this design has important influence to the resulting properties of the circuit. Within the analysis of the circuits have been found, how each current operational amplifier works in a defined current range. Every type of surveyed amplifier is closely described, the internal structure is depicted and graph of current transmission of amplifier is shown. At the end of this thesis the amplifiers are compared and there are introduced their advantages and disadvantages.

The thesis deals about method of gain signals from strain gauge bridges. There are mentioned some signal conditioning methods for bridges amplifiers and charactered their properties. In the next part of this thesis are calculated the amplifier errors for various temperature. There are projected individual variants of strain gage amplifiers (instrumentation amplifier AD524, isolation amplifier, switched capacitor based instrumentation amplifier), their properties are compared with strain gage amplifier Vishay P-3500.

An accurate, high-speed, fully differential difference amplifier for current sensing utilizing the chopper approach was implemented in a 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. Unlike state-of-the-art solutions, we use a higher chopping frequency in the MHz range due to the bandwidth requirements of the introduced circuits for the latter application, namely, low-side phase-current measurement in motor control circuits. Except the low-pass filter (LPF) effect of the output stage, no additional LPF was integrated in hardware at the output of the circuits. We show that on the other hand a digital LPF, which can be integrated in the field-programmable gate-array (FPGA) logic or microcontroller used for the motor control, offers a higher flexibility in terms of filter design. Weak input signals of only few mV can be reconstructed with a high accuracy. This is demonstrated for a 500 kHz rectangular signal and a chopping frequency of 20 MHz. Note that an input-signal frequency of several hundreds of kHz with harmonics in the MHz region is very challenging for chopper amplifiers. Still, a significant decrease of the input-referred noise is demonstrated, especially cancelling out the 1/f-noise achieving a remaining noise floor of approximately 8.5 nV/√Hz. Overall, the input-referred noise level can be pushed far below 50 μV (root mean square). Moreover, using a quite relaxed second-order Butterworth filter with a 3 dB corner frequency of 1 MHz, input-referred noise levels of 10 μV (root mean square) can be easily achieved at the costs of reduced bandwidth. The lowest achieved input offset is 50 μV. The gain is adjusted by resistive feedback and is approximately 40 dB. Hence, the amplifier is suitable for current sensing in motor control circuits, and a significant reduction of the shunt resistance typically used for this purpose will be possible.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / A conventionally designed radio frequency amplifier operated in its linear region exhibits low DC to RF conversion efficiency. Typically, for a power amplifier designed for digital modulation applications, the amplifier is operated “backed-off” from its P1dB point by a factor of 10 or -10 dB. The typical linear amplifier is biased for either Class A or Class A/B operation depending on the acceptable design trade-offs between efficiency and linearity between these two methods. A novel design approach to increasing the efficiency of a linear RF power amplifier using a modified Odd-Way Doherty technique is presented in this paper. The design was simulated, built and then tested. The design yields improvements in efficiency and linearity.

Os sistemas ópticos atuais, baseados em fibras monomodo, operam próximos ao limite teórico da capacidade. Sistemas ópticos baseados em multiplexação modal (Mode Division Multiplexing – MDM) possibilitam o aumento da capacidade do sistema por meio do uso de fibras de poucos modos. Nestes sistemas, a propriedade de ortogonalidade entre os modos propagantes permite que cada modo espacial carregue um sinal óptico específico. O amplificador à fibra dopada com érbio (Erbium-Doped Fiber Amplifier – EDFA) segue fundamental para assegurar a transmissão em longas distâncias. No entanto, devido às distintas distribuições de intensidade dos modos que compõem o sinal de entrada, cada modo experimenta diferentes valores de ganho. Desta forma, o objetivo principal no projeto de EDFAs de poucos modos (Few-Mode Erbium-Doped Fiber Amplifier – FM-EDFA) é determinar os melhores parâmetros opto-geométricos da fibra para produzir uma amplificação eficiente. A metodologia normalmente empregada é baseada na resolução das equações de taxa e de propagação. Nesta tese, é proposta uma metodologia alternativa de projeto de FM-EDFA, baseada em uma nova figura de mérito. Este parâmetro quantifica o nível de inversão da população dos íons na fibra a partir da integral de superposição (overlap integral), considerando tanto o perfil de dopagem da fibra dopada com érbio para poucos modos (Few-Mode Erbium-Doped Fiber – FM-EDF) quanto as distribuições de intensidade dos sinais de entrada e de bombeio. A aplicação desta metodologia permite reduzir, em cerca de 25-40 vezes, o número de resoluções das equações de taxa e de propagação e, consequentemente, diminuir o tempo de processamento e reduzir o esforço computacional. Como consequência da maior velocidade de processamento, torna-se possível a aplicação de métodos de otimização mais rigorosos, permitindo uma busca em um espaço irrestrito de soluções. Especificamente, a partir de uma metodologia baseada em algoritmos genéticos, obteve-se um perfil de dopagem otimizado. É também demonstrado que os perfis com geometria circular exibem melhores características, como excelente desempenho do FM-EDFA e maior facilidade de fabricação. Por meio da análise da figura de mérito, é mostrado que o desempenho do FM-EDFA é afetado pelas características do modo de bombeio. Finalmente, o desempenho de um sistema óptico MDM é avaliado, simulado por meio da integração entre as ferramentas MatLab® e VPItransmissionMakerTM, comprovando a necessidade do projeto de um amplificador específico para sistemas MDM. / Modern optical systems based on single-mode fiber, operate close to the theoretical capacity limit. By using few-mode fibers, optical systems based on modal division multiplexing (MDM) allows increased system capacity. In these systems, orthogonality between the propagating modes allows each spatial mode to carry a specific optical signal. The erbium doped fiber amplifier (EDFA) remains essential to ensure long distance transmission. However, due to the distinct intensity profile distributions of the modes which comprise the input signal, each mode experiences a different value of optical gain. Thus, the main objective in the few-mode EDFA design (FM-EDFA) is to determine the best opto-geometrical fiber parameters in order to produce an efficient amplification. The methodology normally used is based on the simultaneous resolution of the rate and propagation equations. In this thesis, we propose an alternative methodology for the FM-EDFA design, based on a new figure of merit which quantifies the level of population inversion for the Er ions in the fiber, by means of a overlap integral considering both the doping profile of the few-mode erbium doped fiber (FM-EDF) as well as the intensity distributions of the optical signals and pump beams. This methodology reduces, by a factor of 25-40, the number of resolutions of the rate and propagation equations, thereby decreasing processing time and computational effort. As a consequence of the improved processing speed, it becomes possible to apply more rigorous optimization methods in an unrestricted solution space. Specifically, by using a genetic algorithm technique, we obtained an optimized doping profile. It is also shown that profiles with circular geometry exhibit improved features, such as excellent FM-EDFA performance and ease of manufacturing. By analyzing the figure of merit, it is shown that the FM-EDFA performance is affected by the characteristics of the pump mode. Finally, the performance of an MDM optical system is evaluated, by integrating Matlab and VPI simulation tools, to demonstrate the need for specific amplifier designs in MDM systems.

Cette thèse porte sur la conception d'un circuit intégré CMOS pour l'électronique de lecture de capteurs bolométriques à base de semiconducteurs ou supraconducteurs haute-température. Dans ce manuscrit, une chaîne de traitement du signal est étudiée. Elle est composée d'un amplificateur différentiel à gain fixé pour des températures de 40 à 400K, ainsi que d'un filtre de fréquence passe-bas actif à haute dynamique. Une architecture optimale d'amplificateur est définie sans contre-réaction, permettant d'atteindre une large bande passante (17MHz pour un gain de 40dB), une consommation réduite (Iq = 2mA) et une haute impédance d'entrée. Afin de fixer le gain avec précision dans la structure CMOS, deux méthodes différentes sont présentées et vérifiées sur un circuit intégré. Par la suite, le comportement des filtres dans la bande d'atténuation est étudié afin d'augmenter la fréquence de coupure maximale. Deux structures avec une faible influence des éléments actifs « réels » sont conçues: le filtre Sallen-Key amélioré et la structure basée sur un convoyeur du courant CCII-. Enfin, nous présentons un CCII- intégré en CMOS ayant une très faible impédance de sortie.

Designing CMOS linear transmitter front-end, specially the power amplifiers (PAs), in multi-band wireless transceivers is a major challenge for the single-chip integration of a CMOS radio. In some of the linear PA systems, for example, polar- or predistortion-PA system, amplitude and phase control circuits are used to suppress the distortion produces by the PA core. The requirements of these controlling circuits are much different from their conventional role in a receiver or a phase array system. In this dissertation, the special design issues will be addressed, and the circuit topologies of the amplitude and phase controllers will be proposed. In attempt to control the high-power input signal of a PA system, a highly linear variable attenuator with adaptive body biasing is first introduced. The voltage swing on the signal path is intentionally coupled to the body terminal of the triple-well NMOS devices to reduce their impedance variation. The fabricated variable attenuator shows a significant improvement on linearity as compared to previous CMOS works. The results of this research are then used to build a variable gain amplifier for linear PA systems that requires gain of its amplitude tuning circuits. Different from the conventional attenuator-based VGAs, the high linearity of the suggested attenuator allows it to be put after the gain stage in the presented VGA topology. This arrangement along with the current boosting technique gives the VGA a better noise performance while having a linear-in-dB tuning curve and better worst-case linearity. The following part of the dissertation is about a compact, linear-in-degree tuned variable phase shifter as the phase controller in the PA system. This design uses a modified RC poly-phase filter to produce a set of an orthogonal phase vectors with smaller loss. A specially designed control circuit combines these vectors and generates an output signal with different phases, while having very small gain mismatches at different phase setting. The proposed amplitude and phase control circuits are then verified with a system level analysis. The results show that the proposed designs successfully reduce the non-linear effect of a wireless transmitter.

Os sistemas ópticos atuais, baseados em fibras monomodo, operam próximos ao limite teórico da capacidade. Sistemas ópticos baseados em multiplexação modal (Mode Division Multiplexing – MDM) possibilitam o aumento da capacidade do sistema por meio do uso de fibras de poucos modos. Nestes sistemas, a propriedade de ortogonalidade entre os modos propagantes permite que cada modo espacial carregue um sinal óptico específico. O amplificador à fibra dopada com érbio (Erbium-Doped Fiber Amplifier – EDFA) segue fundamental para assegurar a transmissão em longas distâncias. No entanto, devido às distintas distribuições de intensidade dos modos que compõem o sinal de entrada, cada modo experimenta diferentes valores de ganho. Desta forma, o objetivo principal no projeto de EDFAs de poucos modos (Few-Mode Erbium-Doped Fiber Amplifier – FM-EDFA) é determinar os melhores parâmetros opto-geométricos da fibra para produzir uma amplificação eficiente. A metodologia normalmente empregada é baseada na resolução das equações de taxa e de propagação. Nesta tese, é proposta uma metodologia alternativa de projeto de FM-EDFA, baseada em uma nova figura de mérito. Este parâmetro quantifica o nível de inversão da população dos íons na fibra a partir da integral de superposição (overlap integral), considerando tanto o perfil de dopagem da fibra dopada com érbio para poucos modos (Few-Mode Erbium-Doped Fiber – FM-EDF) quanto as distribuições de intensidade dos sinais de entrada e de bombeio. A aplicação desta metodologia permite reduzir, em cerca de 25-40 vezes, o número de resoluções das equações de taxa e de propagação e, consequentemente, diminuir o tempo de processamento e reduzir o esforço computacional. Como consequência da maior velocidade de processamento, torna-se possível a aplicação de métodos de otimização mais rigorosos, permitindo uma busca em um espaço irrestrito de soluções. Especificamente, a partir de uma metodologia baseada em algoritmos genéticos, obteve-se um perfil de dopagem otimizado. É também demonstrado que os perfis com geometria circular exibem melhores características, como excelente desempenho do FM-EDFA e maior facilidade de fabricação. Por meio da análise da figura de mérito, é mostrado que o desempenho do FM-EDFA é afetado pelas características do modo de bombeio. Finalmente, o desempenho de um sistema óptico MDM é avaliado, simulado por meio da integração entre as ferramentas MatLab® e VPItransmissionMakerTM, comprovando a necessidade do projeto de um amplificador específico para sistemas MDM. / Modern optical systems based on single-mode fiber, operate close to the theoretical capacity limit. By using few-mode fibers, optical systems based on modal division multiplexing (MDM) allows increased system capacity. In these systems, orthogonality between the propagating modes allows each spatial mode to carry a specific optical signal. The erbium doped fiber amplifier (EDFA) remains essential to ensure long distance transmission. However, due to the distinct intensity profile distributions of the modes which comprise the input signal, each mode experiences a different value of optical gain. Thus, the main objective in the few-mode EDFA design (FM-EDFA) is to determine the best opto-geometrical fiber parameters in order to produce an efficient amplification. The methodology normally used is based on the simultaneous resolution of the rate and propagation equations. In this thesis, we propose an alternative methodology for the FM-EDFA design, based on a new figure of merit which quantifies the level of population inversion for the Er ions in the fiber, by means of a overlap integral considering both the doping profile of the few-mode erbium doped fiber (FM-EDF) as well as the intensity distributions of the optical signals and pump beams. This methodology reduces, by a factor of 25-40, the number of resolutions of the rate and propagation equations, thereby decreasing processing time and computational effort. As a consequence of the improved processing speed, it becomes possible to apply more rigorous optimization methods in an unrestricted solution space. Specifically, by using a genetic algorithm technique, we obtained an optimized doping profile. It is also shown that profiles with circular geometry exhibit improved features, such as excellent FM-EDFA performance and ease of manufacturing. By analyzing the figure of merit, it is shown that the FM-EDFA performance is affected by the characteristics of the pump mode. Finally, the performance of an MDM optical system is evaluated, by integrating Matlab and VPI simulation tools, to demonstrate the need for specific amplifier designs in MDM systems.