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The goal of this thesis is developing a two-color Ytterbium (Yb) fiber amplifier system that can be used for generation of mid-infrared radiation. Previously, our group reported generating 20 µW of average power, at a wavelength of 18µm. This was accomplished through the amplification of a two color-seed with peaks at 1040nm and 1110nm, through a two stage amplification without any compression. The mid-infrared radiation (MIR) was generated with a 4.5 ps pulse duration by the method of difference-frequency mixing, using 300 mW of average power from the two-color Yb-fiber amplifier. Because there was no limitation by two-photon absorption, MIR output power could be scaled by increasing the amplifier power. The current project aims to increase the peak power of the laser pulses to improve the efficiency of the nonlinear mixing. The two-colour seed is generated by continuum generation in a photonic crystal fibre, pumped by 200 mW of average power from a mode-locked Yb:fibre laser. In order to efficiently increase the energy of the two wavelengths, the 4.6 mW seed pulse is now pre-amplified up to 21 mW in a 2.7 m length single mode, single core Yb:fibre . The pre-amplifier used a double-ended pumping scheme with two single mode diode lasers at 976 nm each having 150 mW maximum pump power. A notch filter was placed in the output beam to eliminate any Amplified Spontaneous Emission. After further amplification in a 7 m length of double clad, Yb-fibre, a maximum average power of 727 mW was achieved for two colours peaked at 1035 nm and 1105 nm wavelengths. The pump power for this stage was 6 W. A grating stretcher is now used to select the two-colour input along with stretching the pulses. A three grating compressor is used to compress the output pulses to 466 fs pulse duration. After compression the average power of the two colours is 350 and 110 mW for wavelengths at 1035 and 1105nm, respectively. These higher power pulses are planned to be used to increase the mid-infrared generation efficiency.

The goal of this thesis is developing a two-color Ytterbium (Yb) fiber amplifier system that can be used for generation of mid-infrared radiation. Previously, our group reported generating 20 µW of average power, at a wavelength of 18µm. This was accomplished through the amplification of a two color-seed with peaks at 1040nm and 1110nm, through a two stage amplification without any compression. The mid-infrared radiation (MIR) was generated with a 4.5 ps pulse duration by the method of difference-frequency mixing, using 300 mW of average power from the two-color Yb-fiber amplifier. Because there was no limitation by two-photon absorption, MIR output power could be scaled by increasing the amplifier power. The current project aims to increase the peak power of the laser pulses to improve the efficiency of the nonlinear mixing. The two-colour seed is generated by continuum generation in a photonic crystal fibre, pumped by 200 mW of average power from a mode-locked Yb:fibre laser. In order to efficiently increase the energy of the two wavelengths, the 4.6 mW seed pulse is now pre-amplified up to 21 mW in a 2.7 m length single mode, single core Yb:fibre . The pre-amplifier used a double-ended pumping scheme with two single mode diode lasers at 976 nm each having 150 mW maximum pump power. A notch filter was placed in the output beam to eliminate any Amplified Spontaneous Emission. After further amplification in a 7 m length of double clad, Yb-fibre, a maximum average power of 727 mW was achieved for two colours peaked at 1035 nm and 1105 nm wavelengths. The pump power for this stage was 6 W. A grating stretcher is now used to select the two-colour input along with stretching the pulses. A three grating compressor is used to compress the output pulses to 466 fs pulse duration. After compression the average power of the two colours is 350 and 110 mW for wavelengths at 1035 and 1105nm, respectively. These higher power pulses are planned to be used to increase the mid-infrared generation efficiency.

Different wireless communication systems utilizing different standards and for multiple applications have penetrated the normal people's life, such as Cell phone, Wireless LAN, Bluetooth, Ultra wideband (UWB) and WiMAX systems. The wireless receiver normally serves as the primary part of the system, which heavily influences the system performance. This research concentrates on the designs of several important blocks of the receiver; multi-stage amplifier and low noise amplifier. Two novel multi-stage amplifier typologies are proposed to improve the bandwidth and reduce the silicon area for the application where a large capacitive load exists. They were designed using AMI 0.5 m µ CMOS technology. The simulation and measurement results show they have the best Figure-of-Merits (FOMs) in terms of small signal and large signal performances, with 4.6MHz and 9MHz bandwidth while consuming 0.38mW and 0.4mW power from a 2V power supply. Two Low Noise Amplifiers (LNAs) are proposed, with one designed for narrowband application and the other for UWB application. A noise reduction technique is proposed for the differential cascode Common Source LNA (CS-LNA), which reduces the LNA Noise Figure (NF), increases the LNA gain, and improves the LNA linearity. At the same time, a novel Common Gate LNA (CG-LNA) is proposed for UWB application, which has better linearity, lower power consumption, and reasonable noise performance. Finally a novel practical current injection built-in-test (BIT) technique is proposed for the RF Front-end circuits. If the off-chip component Lg and Rs values are well controlled, the proposed technique can estimate the voltage gain of the LNA with less than 1dB (8%) error.

The first topic of this thesis presents a novel VGA (variable gain amplifier) design which is applied in the AGC (automatic gain control) loop of digital video broadcasting - terrestrial (DVB-T) receivers. A total of three digital variable gain amplifiers (DVGA) are cascaded to provide a 70 dB dynamic range and 95 MHz operation frequency. The proposed digital VGA implemented by 0.35um 2P4M CMOS technology possesses 70 dB dynamic tuning range with a 0.3 dB gain error and 95 MHz bandwidth, and the power consumption is found to be 32.7 mW given a 3.3 V power supply. The second topic presents a design of a 60 ps peak-to-peak jitter, 80MHz, phase-locked loop (PLL) circuit for DVB-T receivers. The simulation results using the TSMC (Taiwan Semiconductor Manu-facturing Company) 0.35um 2P4M CMOS process show that the proposed PLL achieves as low as 60 ps peak-to-peak jitter when the output frequency is 80 MHz and the power consumption is merely 10.5 mW given a 3.3 V power supply.

The design of a low distortion and high efficiency self-oscillating power amplifier is presented. It is designed using TSMC 0.35µm, 2p4m CMOS technology. We use noise shaping to reduce the THD (Total Harmonic Distortion). This design can be applied to hearing aids. The supply voltage is 1.5V for hearing aids. Experimental results demonstrate that the proposed amplifier has the total harmonic distortion (THD) of 0.0751% and power efficiency around 90.1%. Measurement result reveals that this circuit can be up to 0.25% of the THD and 89.7% of the power efficiency. This result shows that the proposed power amplifier has superior performance in THD and power efficiency, and this circuit is applicable to low-distortion, high-efficiency, and low-voltage applications, such as the hearing aids.

A low noise signal acquisition protocol is required for inner ear evoked response recordings. In this work, a parallel amplifier approach was investigated to implement a bio-signal amplifier with low voltage noise (<5nV/√Hz), and low current noise (~2fA/√Hz). A modified ear electrode was investigated to reduce biological interference and thermal noise due to high impedance electrodes. A physical model to simulate electrical activity of the inner ear was developed to evaluate the accuracy of detecting vestibular field potentials (FPs) in the presence of various noise sources. Muscle activity and noise generated from the recording apparatus were found to be the dominating sources, degrading performance of FP extraction. Contributions from this work include: the design, implementation, and validation of a bio-signal amplifier with <5nV/√Hz voltage noise, and a low impedance electrode development and placement protocol. As a result, a signal-to-noise-ratio improvement of ~11dB (compared to the current protocol) was achieved.

A low noise signal acquisition protocol is required for inner ear evoked response recordings. In this work, a parallel amplifier approach was investigated to implement a bio-signal amplifier with low voltage noise (<5nV/√Hz), and low current noise (~2fA/√Hz). A modified ear electrode was investigated to reduce biological interference and thermal noise due to high impedance electrodes. A physical model to simulate electrical activity of the inner ear was developed to evaluate the accuracy of detecting vestibular field potentials (FPs) in the presence of various noise sources. Muscle activity and noise generated from the recording apparatus were found to be the dominating sources, degrading performance of FP extraction. Contributions from this work include: the design, implementation, and validation of a bio-signal amplifier with <5nV/√Hz voltage noise, and a low impedance electrode development and placement protocol. As a result, a signal-to-noise-ratio improvement of ~11dB (compared to the current protocol) was achieved.

Orientador: Carlos Alberto dos Reis Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T10:35:49Z (GMT). No. of bitstreams: 1 Santos_FilipedeAndradeTabarani_M.pdf: 11362655 bytes, checksum: 2e42c97ddd2bc2cb397c41f31568dc37 (MD5) Previous issue date: 2011 / Resumo: Este trabalho apresenta o estudo aprofundado e a confecção de amplificadores realimentados por corrente (CFA). São analisadas as principais características de um CFA e comparado com o amplificador realimentado por tensão (VOA). Buscou-se esclarecer as aplicações nas quais a primeira célula apresenta-se como melhor alternativa e como importante ferramenta a ser disponibiliza aos projetistas. Ao longo desta analise são frisadas as principais dificuldades na implementação da célula em tecnologia CMOS mencionando as soluções encontradas pela na literatura. Estas dificuldades impedem a confecção de CFAs CMOS comerciais. Um dos principais problemas da implementação de amplificadores realimentados por corrente em tecnologia CMOS e a baixa transcondutância dos transistores. A literatura propõe contornar esta deficiência da tecnologia utilizando células que obtêm alta transcondutância através do uso de realimentação interna [1]. Entretanto, a topologia proposta possui um severo compromisso entre transcondutância e banda de freqüência. O trabalho apresentado nesta dissertação deixa sua contribuição a literatura propondo dois métodos para amenizar este compromisso, que resultam no deslocamento da freqüência de -3dB, tornando-a significantemente maior que a original. No exemplo de projeto, aqui ilustrado, foi obtida banda 3,25 vezes a original,mantendo as características DC.O projeto de duas topologias, sendo uma baseada no primeiro CFA monolítico comercializado e a outra que utiliza transistores compostos, foi realizado visando a implementação monolítica em tecnologia 0,35 ?m CMOS da fabrica Austriamicrosystems. Os protótipos fabricados foram medidos e os resultados comparados com o esperado por simulação / Abstract: This work presents the study and design of current-feedback amplifiers (CFA).It is analyzed the main characteristics of a CFA as it compares to a typical voltage feedback amplifier (VOA). It was attempted to clarify in which applications the first mentioned cell excels at and why it can serve as an important tool for the designers. Throughout the analysis, the main difficulties regarding the implementation of the cell using CMOS technology are highlighted and the solutions proposed by the literature exposed. Those characteristics restrain the conception of CMOS commercials CFAs. One of the primary obstacles for the implementation of current-feedback amplifiers using CMOS technology is the low transconductance of the transistors. The literature proposes the use of cells with internal feedback in order to solve this issue [1].However, the proposed cell has a severe trade-off between transconductance and frequency bandwidth. This work provides its contribution to the literature by proposing two methods to loosen this trade-off. Using the proposed modification, it was obtained 3.25 times the original bandwidth while maintaining all of its native DC characteristics. The design of two topologies was carried out using monolithic Austriamicrosystems0.35?m CMOS technology; one based on the topology of the first commercialized monolithic CFA and the other using compound transistors. The produced prototypes were measured and the results compared with expected by simulation / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

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