Accurate Settling-Time Modeling and Design Procedures for Two-Stage Miller-Compensated Amplifiers for Switched-Capacitor Circuits

We present modeling techniques for accurate estimation of settling errors in switched-capacitor (SC) circuits built with Miller-compensated operational transconductance amplifiers (OTAs). One distinctive feature of the proposal is the computation of the impact of signal levels (on both the model parameters and the model structure) as they change during transient evolution. This is achieved by using an event-driven behavioral approach that combines small- and large-signal behavioral descriptions and keeps track of the amplifier state after each clock phase. Also, SC circuits are modeled under closed-loop conditions to guarantee that the results remain close to those obtained by electrical simulation of the actual circuits. Based on these models, which can be regarded as intermediate between the more established small-signal approach and full-fledged simulations, design procedures for dimensioning SC building blocks are presented whose targets are system-level specifications (such as ENOB and SNDR) instead of OTA specifications. The proposed techniques allow to complete top-down model-based designs with 0.3-b accuracy.Ministerio de Educación y Ciencia TEC2006-03022Junta de Andalucía TIC-0281

Transistor-Level Synthesis of Pipeline Analog-to-Digital Converters Using a Design-Space Reduction Algorithm

A novel transistor-level synthesis procedure for pipeline ADCs is presented. This procedure is able to directly map high-level converter specifications onto transistor sizes and biasing conditions. It is based on the combination of behavioral models for performance evaluation, optimization routines to minimize the power and area consumption of the circuit solution, and an algorithm to efficiently constraint the converter design space. This algorithm precludes the cost of lengthy bottom-up verifications and speeds up the synthesis task. The approach is herein demonstrated via the design of a 0.13 μm CMOS 10 bits@60 MS/s pipeline ADC with energy consumption per conversion of only 0.54 pJ@1 MHz, making it one of the most energy-efficient 10-bit video-rate pipeline ADCs reported to date. The computational cost of this design is of only 25 min of CPU time, and includes the evaluation of 13 different pipeline architectures potentially feasible for the targeted specifications. The optimum design derived from the synthesis procedure has been fine tuned to support PVT variations, laid out together with other auxiliary blocks, and fabricated. The experimental results show a power consumption of 23 [email protected] V and an effective resolution of 9.47-bit@1 MHz. Bearing in mind that no specific power reduction strategy has been applied; the mentioned results confirm the reliability of the proposed approach.Ministerio de Ciencia e Innovación TEC2009-08447Junta de Andalucía TIC-0281

A Radiation-Hard Dual Channel 4-bit Pipeline for a 12-bit 40 MS/s ADC Prototype with extended Dynamic Range for the ATLAS Liquid Argon Calorimeter Readout Electronics Upgrade at the CERN LHC

The design of a radiation-hard dual channel 12-bit 40 MS/s pipeline ADC with extended dynamic range is presented, for use in the readout electronics upgrade for the ATLAS Liquid Argon Calorimeters at the CERN Large Hadron Collider. The design consists of two pipeline A/D channels with four Multiplying Digital-to-Analog Converters with nominal 12-bit resolution each. The design, fabricated in the IBM 130 nm CMOS process, shows a performance of 68 dB SNDR at 18 MHz for a single channel at 40 MS/s while consuming 55 mW/channel from a 2.5 V supply, and exhibits no performance degradation after irradiation. Various gain selection algorithms to achieve the extended dynamic range are implemented and tested.Comment: 22 pages, 22 figures, accepted by JINS

700mV low power low noise implantable neural recording system design

This dissertation presents the work for design and implementation of a low power, low noise neural recording system consisting of Bandpass Amplifier and Pipelined Analog to Digital Converter (ADC) for recording neural signal activities. A low power, low noise two stage neural amplifier for use in an intelligent Radio-Frequency Identification (RFID) based on folded cascode Operational Transconductance Amplifier (OTA) is utilized to amplify the neural signals. The optimization of the number of amplifier stages is discussed to achieve the minimum power and area consumption. The amplifier power supply is 0.7V. The midband gain of amplifier is 58.4dB with a 3dB bandwidth from 0.71 to 8.26 kHz. Measured input-referred noise and total power consumption are 20.7 μVrms and 1.90 μW respectively. The measured result shows that the optimizing the number of stages can achieve lower power consumption and demonstrates the neural amplifier's suitability for instu neutral activity recording. The advantage of power consumption of Pipelined ADC over Successive Approximation Register (SAR) ADC and Delta-Sigma ADC is discussed. An 8 bit fully differential (FD) Pipeline ADC for use in a smart RFID is presented in this dissertation. The Multiplying Digital to Analog Converter (MDAC) utilizes a novel offset cancellation technique robust to device leakage to reduce the input drift voltage. Simulation results of static and dynamic performance show this low power Pipeline ADC is suitable for multi-channel neural recording applications. The performance of all proposed building blocks is verified through test chips fabricated in IBM 180nm CMOS process. Both bench-top and real animal test results demonstrate the system's capability of recording neural signals for neural spike detection

Design of Low-Voltage High-Performance Sample and Hold Circuit in 0.18μm CMOS Technology

Over the last two decade, digital signal processing (DSP) has grown rapidly in electronic systems to provide more reconfigureability and programmability in the applications, compared to analog component, which allows easier design and test automation. Digital circuit usage is increasing because of scaling properties of very large scale integration (VLSI) processes. This has allowed new generation of digital circuit to attain higher speed, more functionality per chip, low power dissipation, lower cost. Analog world, analog to digital converter (ADC) are used to convert the signal from analog to digital domain. For interfacing with DSP sample and hold (S/H) circuit is a key building block in, and is often used in front end of the ADCs to relax their timing requirement. The function of S/H circuit is to take samples to its input signal and hold these samples in its output for some period of time. The analog circuits in low voltage and low power have assumed great significance due to mixed-mode design required for modern electronic gadgets that demand portability and little power consumption. The mixed mode circuit has existence of both analog and digital circuits on the same chip and it is possible to have low voltage digital circuit in modern scaled-down technologies. However the same is not always true with analog circuits due to the constrains of device noise level and threshold voltage (VT) of MOSFET. Thus for analog circuit to co-exist on the same substrate along with digital system and share same supply voltage, the operation of analog circuit in low voltage environment is essential. The objective of this research is to design a low-voltage, high-performance S/H circuit that will address the above problems. A typical switch capacitor S/H circuit needs amplifier, switches and capacitor. New amplifier have been designed by using the architecture of single stage fully differential folded cascode low voltage operation transconductance amplifier (OTA) which has high gain and speed; the gin boosting technique was used for purpose of increasing the gain of the OTA. This technique does not affect the speed of the single stage. The transmission gate switches using CMOS devices, which have higher linearity and higher speed over a single MOS switch, have been designed for use in the S/H circuit. The switches are operated by clock generator with two non overlapping clock signals having low rise and fall time offering low noise for the S/H circuit. The clock was designed with 77.17ps rise and fall time to reduce the errors of driving MOS switches which results in higher linearity. The S/H circuit was designed to operate with 1.8V supply voltage in 0.18um technology. The sampling rate is 40MSPS with spurious free dynamic range (SFDR) 65.7dB and SNR 70dB

A very low power and low signal 5 bit 50 M samples/s double sampling pipelined ADC for Monolithic Active Pixel Sensors in high energy physics and biomedical imaging applications

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