Information Capacity and Power Efficiency in Operational Transconductance Amplifiers

Information capacity is a fundamental and quantitative bound on the ability of a physical system to communicate information. The capacity depends only on the physical properties of the channel, such as bandwidth, noise, and constraints on the signal values; it does not depend on specific tasks for which the channel may be used. Real analog systems possess intrinsic physical noise such as thermal noise and flicker noise and inevitably suffer degradation of information content. We investigate the information transmission and information-power efficiency of an Operational Transconductance Amplifier (OTA). We present empirical results for the information capacity of an integrated OTA and compare these results with our theoretical model. We notice a significant increase in information content if the system is operated in spectral regions with higher frequency and lower noise level

Time-domain optimization of amplifiers based on distributed genetic algorithms

Thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Electrical and Computer EngineeringThe work presented in this thesis addresses the task of circuit optimization, helping the designer facing the high performance and high efficiency circuits demands of the market and technology evolution. A novel framework is introduced, based on time-domain analysis, genetic algorithm optimization, and distributed processing. The time-domain optimization methodology is based on the step response of the amplifier. The main advantage of this new time-domain methodology is that, when a given settling-error is reached within the desired settling-time, it is automatically guaranteed that the amplifier has enough open-loop gain, AOL, output-swing (OS), slew-rate (SR), closed loop bandwidth and closed loop stability. Thus, this simplification of the circuit‟s evaluation helps the optimization process to converge faster. The method used to calculate the step response expression of the circuit is based on the inverse Laplace transform applied to the transfer function, symbolically, multiplied by 1/s (which represents the unity input step). Furthermore, may be applied to transfer functions of circuits with unlimited number of zeros/poles, without approximation in order to keep accuracy. Thus, complex circuit, with several design/optimization degrees of freedom can also be considered. The expression of the step response, from the proposed methodology, is based on the DC bias operating point of the devices of the circuit. For this, complex and accurate device models (e.g. BSIM3v3) are integrated. During the optimization process, the time-domain evaluation of the amplifier is used by the genetic algorithm, in the classification of the genetic individuals. The time-domain evaluator is integrated into the developed optimization platform, as independent library, coded using C programming language. The genetic algorithms have demonstrated to be a good approach for optimization since they are flexible and independent from the optimization-objective. Different levels of abstraction can be optimized either system level or circuit level. Optimization of any new block is basically carried-out by simply providing additional configuration files, e.g. chromosome format, in text format; and the circuit library where the fitness value of each individual of the genetic algorithm is computed. Distributed processing is also employed to address the increasing processing time demanded by the complex circuit analysis, and the accurate models of the circuit devices. The communication by remote processing nodes is based on Message Passing interface (MPI). It is demonstrated that the distributed processing reduced the optimization run-time by more than one order of magnitude. Platform assessment is carried by several examples of two-stage amplifiers, which have been optimized and successfully used, embedded, in larger systems, such as data converters. A dedicated example of an inverter-based self-biased two-stage amplifier has been designed, laid-out and fabricated as a stand-alone circuit and experimentally evaluated. The measured results are a direct demonstration of the effectiveness of the proposed time-domain optimization methodology.Portuguese Foundation for the Science and Technology (FCT

Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

Low-power/high-gain flexible complementary circuits based on printed organic electrochemical transistors

The ability to accurately extract low-amplitude voltage signals is crucial in several fields, ranging from single-use diagnostics and medical technology to robotics and the Internet of Things. The organic electrochemical transistor, which features large transconductance values at low operation voltages, is ideal for monitoring small signals. Its large transconductance translates small gate voltage variations into significant changes in the drain current. However, a current-to-voltage conversion is further needed to allow proper data acquisition and signal processing. Low power consumption, high amplification, and manufacturability on flexible and low-cost carriers are also crucial and highly anticipated for targeted applications. Here, we report low-power and high-gain flexible circuits based on printed complementary organic electrochemical transistors (OECTs). We leverage the low threshold voltage of both p-type and n-type enhancement-mode OECTs to develop complementary voltage amplifiers that can sense voltages as low as 100 $\mu$V, with gains of 30.4 dB and at a power consumption < 2.7 $\mu$W (single-stage amplifier). At the optimal operating conditions, the voltage gain normalized to power consumption reaches 169 dB/$\mu$W, which is > 50 times larger than state-of-the-art OECT-based amplifiers. In a two-stage configuration, the complementary voltage amplifiers reach a DC voltage gain of 193 V/V, which is the highest among emerging CMOS-like technologies operating at supply voltages below 1 volt. Our findings demonstrate that flexible complementary circuits based on printed OECTs define a power-efficient platform for sensing and amplifying low-amplitude voltage signals in several emerging beyond-silicon applications

Design and characterization of low voltage operational amplifiers for smart sensors using low cost CMOS technology

This bachelor thesis brackets the use of different OTA topologies and compares them under the scope of their application as low power comparators and adders for a ΣΔ ADC. This was undertaken under the “Design and characterization of main building blocks for Medical instrumentation ADCs” research project and, more specifically, in the “Design of a Low-IF Sigma-Delta Modulator” section. The researched topologies include a folded cascode, telescopic cascode, class A Miller as well as a class AB Miller. The implementation was performed at transistor level of the for all topologies in a 0.18 μm with original 1.8 V, downscaled to 1.5 V with the goal of reducing power consumption.Ingeniería Biomédic

Low Noise Readout Circuits for Particle and Radiation Sensors

The present thesis follows a three years' work in design, realization and operation of electronic circuits for the readout of particle and radiation sensors, carried out in close collaboration with the Istituto Nazionale di Fisica Nucleare (INFN), sezione di Milano Bicocca. The work was mainly focused to applications in particle physics experiments which are currently in the construction phase, or to existing experiments which planned major hardware upgrades in the next years, involving the design of new front-end circuits. The circuits developed are in principle applicable also outside the field of pure science research, for applications in nuclear instrumentation, medical imaging, security and industrial scanners, and others.Comment: PhD thesis, Universit\`a degli Studi di Firenze, 201