This chapter covers device and circuit aspects of low-power analog CMOS circuit design. The fundamental limits constraining the design of low-power circuits are first recalled with an emphasis on the implications of supply voltage reduction. Biasing MOS transistors at very low current provides new features but requires dedicated models valid in all regions of operation including weak, moderate and strong inversion. Low-current biasing also has a strong influence on noise and matching properties. All these issues are discussed, together with the particular aspects related to passive devices and parasitic effects. The design process has to be supported by efficient and accurate circuit simulation. To this end, the EKV compact MOST model for circuit simulation is shortly presented. The use of the basic concepts such as pinch-off voltage, inversion factor and specific current are highlighted thanks to some very simple but fundamental circuits and to an effective use of the model. New design techniques that are appropriate for low-power and/or low-voltage circuits are presented with an emphasis on the analog floating point technique, the instantaneous companding principle, and their application to filters.

Translinear or log-domain #lters are theoretically exact realisations of linear di#erential equations. However, the dynamical translinear principle can also be applied to the implementation of nonlinear di#erential equations. In this paper, an RMS-DC converter is proposed, comprising a direct implementation of the corresponding nonlinear di#erential equation by means of the dynamical translinear principle. Correct operation of the circuit was veri#ed through measurements. 1 Introduction The translinear principle #1# plays a key role in conventional implementations of RMS-to-DC conversion #2#. A well-known RMS-DC converter is shown in Fig. 1. The squarer-divider basically comprises a four-transistor, i.e. second-order #3#, translinear loop. As the squarer-divider facilitates one-quadrant operation, its input signal is full-wave recti#ed. It calculates the current I 2 in =I out , where I out is the output current of the RMS-DC converter and is equal to the mean value of I 2 in ...

Synapses are a critical element of biologically-realistic, spike-based neural computation, serving the role of communication, computation, and modification. Many different circuit implementations of synapse function exist with different computational goals in mind. In this paper we describe a new CMOS synapse design that separately controls quiescent leak current, synaptic gain, and time-constant of decay. This circuit implements part of a commonly-used kinetic model of synaptic conductance.

Abstract—We introduce a new approach to synthesizing Class AB log-domain filters that satisfy dynamic differential-mode and common-mode constraints simultaneously. Whereas the dynamic differential-mode constraint imposes the desired filtering behavior, the dynamic common-mode constraint solves the zero-dc-gain problem, a shortcoming of previous approaches. Also, we introduce a novel push–pull circuit that serves as a current-splitter; it rectifies a differential signal into the ON and OFF paths in our log-domain filter. As an example, we synthesize a first-order low-pass filter, and, to demonstrate the rejection of dc signals, we implement an adaptive filter by placing this low-pass circuit in a variable-gain negative-feedback path. Feedback gain is controlled by signal energy, which is extracted simply by summing complementary ON and OFF signals—dc signals do not contribute to the signal energy nor are they amplified by the feedback. We implement this adaptive filter design in a silicon chip that draws biological inspiration from visual processing in the mammalian retina. It may also be useful in other applications that require dynamic time-constant adaptation. Index Terms—Adaptive filtering, artificial vision, class AB circuits, neuromorphic engineering.

A promising new approach to shorten the design trajectory of analog integrated circuits without giving up functionality is formed by the class of dynamic translinear circuits. This paper presents a structured design method for this young, yet rapidly developing, circuit paradigm. As a design example, a 40-¯A 2-V dynamic translinear PLL, used as an FM demodulator, is presented. I. Introduction Electronics design can be considered to be the mapping of a set of mathematical functions onto silicon. For discrete-time systems, of which the digital systems today are by far the most popular, this comes down to the implementation of a number of difference equations, whereas for continuous-time systems, often denoted by the term analog, differential equations are the starting points. In mixed analog-digital systems, the analog parts, however, often occupy less than ten percent of the complete, i.e., the mixed analog-digital circuitry, whereas their design trajectory is often substantially longe...

The analysis of the e ects of noise and interference in companding signal processors are discussed. Important di erences from the analysis and e ects encountered in conventional signal processors are pointed out. Finally, the theoretical calculations are successfully compared to experimental results. 1.

Abstract — A simple methodology for implementation of low-order, current-mode, log-domain filters in CMOS technology is presented. The key transistors in the circuit are operated in weak inversion and in contrast with previous approache s may pass into the triode regime. The concept is particularly suited to implementation in silicon-on-insulator technology, because dielectric isolation of the transistors eliminates leakage currents, and because influence of the body effect on circuit function is limited. Very long time constants, on the order of 1s or more, are obtainable. A simple elaboration of the basic unit circuit allows the time constant to be controlled by a bias current.

This report describes the class of static translinear circuits, which are capable of accurately implementing a wide range of static nonlinear relationships in the current signal domain, such as products, quotients, fixed power-law relationships, vector magnitude, and rational functions. After a brief historical account of the emergence of the class of translinear circuits, we examine the representation of information in translinear circuits and systems. Then, we describe the translinear principle and its application to the analysis and synthesis of translinear-loop circuits, illustrating the processes with several example circuits. We then describe the operation and implementation of a translinear-circuit primitive called the multiple-input translinear element (MITE). From such elements, we build MITE networks, a class of low-voltage translinear circuits that is equivalent to the class of translinear-loop circuits. We describe intuitively the operation of MITE networks. We also describe how to analyze and synthesize such circuits, illustrating these processes with several example circuits.

Abstract—Certain issues in the analysis of the effects of noise and interference in instantaneously companding signal processors is discussed. Important differences from the analysis and effects encountered in conventional signal processors are pointed out, and are illustrated by deriving analytical results for deterministic small interference and stationary random noise in a first-order instantaneously companding filter. The theoretical calculations are successfully compared to experimental results. Index Terms—Companding, noise, log-domain filters. I.

Low energy drain is key to the success of portable, battery-operated equipment. If the energy drain per task can be slashed down, battery life can proportionately be increased. Most conventional analog circuits are designed worst-case, for adequate performance while handling the most demanding tasks. This requires large power dissipation; when these circuits are called to perform less demanding tasks, they continue to dissipate the same large power unnecessarily. In other words, in such cases we are stuck with a fixed circuit. The solution is to allow the internal attributes of the circuit to vary, depending on the task at hand. In this article we review several recently proposed techniques that make this possible. We call these circuits internally varying. (We cannot call these circuits Y. Tsividis, N. Krishnapura,