Bøger af Kari A. I. Halonen

For four decades the evolution of integrated circuits has followed Moore's law, according to which the number of transistors per square millimeter of silicon doubles every 18 months. At the same time transistors have become faster, making possible ever-increasing clock rates in digital circuits. This trend seems set to continue for at least another decade without slowing down. Thus, in the near future the processing power of digital circuits will continue to increase at an accelerating pace. For analog circuits the evolution of technology is not as beneficial. Thus, there is a trend to move signal processing functions from the analog domain to the digital one, which, besides allowing for a higher level of accuracy, provides savings in power consumption and silicon area, increases robustness, speeds up the design process, brings flexibility and programmability, and increases the possibilities for design reuse. In many applications the input and output signals of the system are inherently analog, preventing all-digital realizations; at the very least a conversion between analog and digital is needed at the - terfaces. Typically, moving the analog-digital boundary closer to the outside world increases the bit rate across it. In telecommunications systems the trend to boost bit rates is based on - ploying widerbandwidths and a higher signal-to-noise ratio. At the same time radio architectures in many applications are evolving toward software-defined radio, one of the main characteristics of which is the shifting of the anal- digital boundary closer to the antenna.

CMOS Current Amplifiers; Speed versus Nonlinearity is intended as a current-amplifier cookbook containing an extensive review of different current amplifier topologies realisable with modern CMOS integration technologies. The seldom-discussed issue of high-frequency distortion performance is derived for all reviewed amplifier topologies using as simple and intuitive mathematical methods as possible. The topologies discussed are also useful as building blocks for high-performance voltage-mode amplifiers. So the reader can apply the discussed techniques to both voltage- and current-mode analogue integrated circuit design.For the most popular open-loop current-mode amplifier, the second-generation current-conveyor (CCII), a macro model is derived that, unlike other reported macromodels, can accurately predict the common-mode behaviour in differential applications. Similarly, this model is used to describe the nonidealities of several other current-mode amplifiers. With modern low-voltage CMOS-technologies, the current-mode operational amplifier and the high-gain current-conveyor (CCIIINFINITY perform better than various open-loop current-amplifiers. Similarly, unlike with conventional voltage-mode operational amplifiers, the large-signal settling behaviour of these two amplifier types does not degrade as CMOS-processes are scaled down.This book contains application examples with experimental results in three different fields: instrumentation amplifiers, continuous-time analogue filters and logarithmic amplifiers. The instrumentation amplifier example shows that using unmatched off-the-self components very high CMRR can be reached even at relatively high frequencies. As a filter application, two 1 MHz 3rd-order low-pass continuous-time filters are realised with a 1.2 mum CMOS-process. These filters use a differential CCIIINFINITY with linearised, dynamically biased output stages resulting in outstanding performance when compared to most OTA-C filter realisations reported.As an application example of nonlinear circuits, two logarithmic amplifier chips are designed and fabricated. The first circuit, implemented with a 1.2 m BiCMOS-process, uses again a CCII8 and a pn-junction as a logarithmic feedback element. With a CCII8 the constant gain-bandwidth product, typical of voltage-mode operational amplifiers, is avoided resulting in a constant 1 MHz bandwidth within a 60 dB signal amplitude range. The second current-mode logarithmic amplifier, realised in a 1.2 m CMOS-process, is based on piece-wise linear approximation of the logarithmic function. In this logarithmic amplifier, using limiting current amplifiers instead of limiting voltage amplifiers results in exceptionally low temperature dependency of the logarithmic output signal. Additionally, along with this logarithmic amplifier a new current peak detector is developed.

A major advantage of a direct digital synthesizer (DDS) is that its output frequency, phase and amplitude can be precisely and rapidly manipulated under digital processor control. Other inherent DDS attributes include the ability to tune with extremely fine frequency and phase resolution, and to rapidly `hop' between frequencies. These combined characteristics have made the technology popular in military radar and communications systems. In fact, DDS technology was previously applied almost exclusively to high-end and military applications: it was costly, power-hungry, difficult to implement, and required a discrete high speed D/A converter. Due to improved integrated circuit (IC) technologies, they now present a viable alternative to analog-based phase-locked loop (PLL) technology for generating agile analog output frequency in consumer synthesizer applications. It is easy to include different modulation capabilities in the DDS by using digital signal processing (DSP) methods, because the signal is in digital form. By programming the DDS, adaptive channel bandwidths, modulation formats, frequency hopping and data rates are easily achieved. The flexibility of the DDS makes it ideal for signal generator for software radio. The digital circuits used to implement signal-processing functions do not suffer the effects of thermal drift, aging and component variations associated with their analog counterparts. The implementation of digital functional blocks makes it possible to achieve a high degree of system integration. Recent advances in IC fabrication technology, particularly CMOS, coupled with advanced DSP algorithms and architectures are providing possible single-chip DDS solutions to complex communication and signal processing subsystems as modulators, demodulators, local oscillators, programmable clock generators, and chirp generators. The DDS addresses a variety of applications, including cable modems, measurement equipments, arbitrary waveform generators, cellular base stations and wireless local loop base stations. Direct Digital Synthesizers was written to find possible applications for radio communication systems. It will have appeal for wireless and wireline communication engineers, teachers and students.