Current source | EPFL Graph Search

A current source is an electronic circuit that delivers or absorbs an electric current which is independent of the voltage across it. A current source is the dual of a voltage source. The term current sink is sometimes used for sources fed from a negative voltage supply. Figure 1 shows the schematic symbol for an ideal current source driving a resistive load. There are two types. An independent current source (or sink) delivers a constant current. A dependent current source delivers a current which is proportional to some other voltage or current in the circuit. Background |- align="center" |style="padding: 1em 2em 0;"| |style="padding: 1em 2em 0;"| |- align="center" | Voltage source | Current source |- align="center" |style="padding: 1em 2em 0;"| |style="padding: 1em 2em 0;"| |- align="center" | Controlled voltage source | Controlled current source |- align="center" |style="padding: 1em 2em 0;"| |style="padding: 1em 2em 0;"| |- align="center" | Battery of cells | S

SOI mixed-mode design techniques and case studies

Marija Blagojevic

Since the emergence of Silicon On Insulator (SOI) technology the research activities have been concentrated on a detailed analysis of SOI devices and their use in different application fields (low-voltage, low-power circuits, high temperature electronics, digital circuits, etc.). The present thesis deals with low-voltage, low-power mixed-mode design using a SOI technology. The goal is to establish the concepts that allow one to design SOI mixed-mode circuits, and to apply these concepts to the design of fully depleted (FD) and partially depleted (PD) SOI circuits and systems. Two studies have been realized in the scope of this work: a Hall sensor based microsystem design using an experimental FD SOI technology a DRAM design using capacitor-less 1T floating-body PD SOI memory cells. At the beginning of this thesis, two major types of SOI devices are introduced, namely FD and PD devices. The most important properties of these devices are then presented and compared to those of CMOS bulk devices. A design methodology based on design retargeting from bulk to SOI technology is further proposed. This methodology is developed with the aim of being implemented for the design of FD SOI circuits. It consists in using the same device dimensions and bias currents for the bulk and the corresponding FD SOI design. The analysis performed proves that such an approach permits one to obtain better circuit performances using the FD SOI technology. The EKV model is chosen for Spice simulations. For that purpose the extraction of the EKV intrinsic parameters has been performed for the experimental 0.5 μm FD SOI technology. The EKV model card obtained from transistor measurements is implemented straightforwardly for circuit simulations. The first study presented in this thesis is an FD SOI Hall sensor front-end for energy measurement. The mixed-mode microsystem design is completely based on the proposed design methodology. The system level solutions are also included, such as the spinning-current method that serves for reduction of the offset and low frequency noise of the analog front-end, and a high resolution analog-to-digital conversion technique. The integrated microsystem is entirely functional. Furthermore, according to the existing literature, this integrated circuit is the first microsystem completely realized using FD SOI technology. The overall system error that is obtained is less than 1.5 %. During the second part of this work, a novel sensing scheme that exploits an automatic reference generation based on successive approximations has been developed for the PD SOI capacitor-less 1T DRAM. The 1T DRAM reference current is generated by an adjustable current source. The electrical calibration of the reference current is performed using a digital-to-analog converter and successive approximations algorithm. The proposed scheme is evaluated in a 2 kb test chip. The circuit integrated using PD SOI technology contains a 2 kb 1T memory array, as well as automatic reference generators and peripheral circuits. The automatic reference generator comprises current mode sense amplifier, M/3M converter, and successive approximations register. All blocks implemented in the test chip are described in detail, and PD SOI design issues are discussed. A number of experimental results demonstrate the potential of the PD SOI 1T DRAM for future embedded DRAM applications. The measured retention time under holding conditions is higher than 1s. In the continuous read mode, a few hundreds of the read cycles can be performed without a refresh operation. The test chip has a measured access time of 25 ns with a read cycle time of 70 ns.

EPFL2005

A Top-Down, Constraint-Driven Design Methodology for Analog ICs

Edoardo Charbon, Alper Demir

Analog circuit design is often the bottleneck when designing mixed analog-digital systems. A Top-Down, Constraint-Driven Design Methodology for Analog Integrated Circuits presents a new methodology based on a top-down, constraint-driven design paradigm that provides a solution to this problem. This methodology has two principal advantages: (1) it provides a high probability for the first silicon which meets all specifications, and (2) it shortens the design cycle. A Top-Down, Constraint-Driven Design Methodology for Analog Integrated Circuits is part of an ongoing research effort at the University of California at Berkeley in the Electrical Engineering and Computer Sciences Department. Many faculty and students, past and present, are working on this design methodology and its supporting tools. The principal goals are: (1) developing the design methodology, (2) developing and applying new tools, and (3) proving' the methodology by undertaking industrial strength' design examples. The work presented here is neither a beginning nor an end in the development of a complete top-down, constraint-driven design methodology, but rather a step in its development. This work is divided into three parts. Chapter 2 presents the design methodology along with foundation material. Chapters 3-8 describe supporting concepts for the methodology, from behavioral simulation and modeling to circuit module generators. Finally, Chapters 9-11 illustrate the methodology in detail by presenting the entire design cycle through three large-scale examples. These include the design of a current source D/A converter, a Sigma-Delta A/D converter, and a video driver system. Chapter 12 presents conclusions and current research topics. A Top-Down, Constraint-Driven Design Methodology for Analog Integrated Circuits will be of interest to analog and mixed-signal designers as well as CAD tool developers.

Springer Verlag1997

A Top-Down, Constraint-Driven Design Methodology for Analog Integrated Circuits

Edoardo Charbon, Alper Demir

Springer Verlag1999

A Top-Down, Constraint-Driven Design Methodology for Analog ICs

Edoardo Charbon, Alper Demir

Springer Verlag1997

SOI mixed-mode design techniques and case studies

Marija Blagojevic

EPFL2005

A Top-Down, Constraint-Driven Design Methodology for Analog Integrated Circuits

Edoardo Charbon, Alper Demir

Springer Verlag1999