Simplified technique for syllabic companding in log-domain filters

It is shown that when syllabic companding is applied to log-domain filters using dynamic biasing, their large signal linearity can be exploited to eliminate the state variable compensation circuit. Owing to its simplicity, the proposed technique has several advantages over previous approaches     

Dynamic power optimization of active filters with application to zero-IF receivers

This paper describes the use of dynamic impedance scaling and dynamic biasing to dynamically optimize the power dissipation of filters depending on the inband signal level. Transients due to the dynamical changes inside the filter are prevented thanks to the implementation of appropriate switching algorithms. To illustrate the concept, a fifth-order Chebychev low-pass active-RC filter with 100-kHz cutoff frequency, designed for partial channel selection in a zero-IF GSM receiver, is presented. The filter is fabricated in a standard 0.18-/spl mu/m CMOS process and uses a 1.2-V power supply. It consumes 2.22-mA supply current during the presence of the minimum receivable signal. The power dissipation decreases by a factor of 2 as the desired signal strength increases by 3 dB, until it reaches its minimum possible value of 0.46 mW. There are a total of five power settings in the filter.     

Continuous-time filters in telecommunications chips

Analog fully integrated continuous-time filters are reviewed. The important rule of such filters in modern telecommunications is outlined, and several techniques for their implementation in mixed-signal chips are described. The article concludes with a review of techniques at the research stage, which promise to expand the frequency range and reduce power dissipation     

Discrete-time parametric amplification based on a three-terminal MOS varactor: analysis and experimental results

This paper discusses discrete-time parametric amplification based on large-signal operation of a three-terminal MOS varactor. The principle of operation is described in detail and analytical estimates of performance are derived. Detailed measurements are reported for a prototype implemented in standard digital CMOS technology. It is demonstrated that the technique can be used to provide micropower, low-gain, low-noise, large-signal amplification.     

Integrated continuous-time filter design - an overview

The state of the art of continuous-time filter design is reviewed. Several techniques are discussed and compared in terms of performance and implementation feasibility in different fabrication technologies. This review does not aim at historical completeness, but rather emphasizes techniques that have proven their worth in commercial applications. Brief mention is also made of experimental work which, in the opinion of the author, shows promise for the future     

Cancellation of distortion of any order in integrated active RC filters

Recently proposed continuous-time integrated filters are considered, consisting of capacitors, MOS transistors and active elements. It is shown that for some topologies and certain frequency ranges, cancellations can occur for both even- and odd-order nonlinearities, independently of the details of the transistor characteristics.     

Technique for increasing the gain-bandwidth product of n-m.o.s. and p-m.o.s. integrated inverters

A method for increasing the bandwidth of single-channel m.o.s. integrated inverters, with practically no decrease in low-frequency gain, is presented. A 1st-order analysis and computer simulation are included.     

A Continuous-Time Programmable Digital FIR Filter

In this paper, we describe the design and implementation of a continuous-time finite-impulse-response processor chain, which includes a 6-bit asynchronous ADC, an asynchronous digital core, and an 8-bit asynchronous DAC designed in TSMC 0.25-mum technology. The continuous-time, discrete-amplitude systems combine benefits associated with analog and digital systems. Discrete-amplitude representations leverage the noise immunity and robustness of digital implementations. Continuous-time, nonsampled operation prevents aliasing and reduces the in-band quantization noise associated with the aliasing of subharmonic components. We present measurement results demonstrating an audio low-pass filter with a bandwidth of 6.0 kHz     

On the small-signal behaviour of the MOS transistor in quasistatic operation

A complete MOST small signal model is proposed, chosen to related most easily to widely used incomplete models. For quasistatic operation, expressions for the model parameters valid for all regions of operation, including weak and moderate inversion, are derived. The predicted bias dependence of the nine model capacitance coefficients, derived starting from the long channel MOST theory recently presented by F. Van de Wiele, is presented and compared to available experimental data.     

MOSFET modeling for analog circuit CAD: problems and prospects

The requirements for good MOSFET modeling are discussed, as they apply to usage in analog and mixed analog-digital design. A set of benchmark tests that can be easily performed by the reader are given, and it is argued that most CAD models today cannot pass all the tests, even for simple, long-channel devices at room temperature. A number of other problems are discussed, and in certain cases specific cures are suggested. The issue of parameter extraction is addressed. Finally, the context of model development and usage is considered, and it is argued that some of the factors responsible for the problems encountered in the modeling effort are of a nontechnical nature