1,721,006 research outputs found
Subsampling models of bandwidth mismatch for time-interleaved converter calibration
No full textBandwidth mismatch is one of the mechanisms that reduce linearity in time-interleaved analog-to-digital converters (TI-ADCs). Models of bandwidth mismatch have been already proposed in the literature: this brief extends them to subsampling signals, validates them against circuit-level simulations, and investigates their effect on linearity in subsampling applications. The effectiveness of two previously published calibration algorithms for the correction of bandwidth mismatch is shown. The proposed models can thus be used to simulate subsampling TI-ADCs and their calibration algorithms
Behavioral Modeling for Calibration of Pipeline Analog-To-Digital Converters
No full textIn this paper, a design flow for the design of calibrated pipeline analog-to-digital converters (ADCs), and a framework for their behavioral modeling is presented. The model includes also second order effects such as nonlinearities and linear and nonlinear memory errors, thus allowing fast and accurate simulations of the ADC behavior. In this way, background calibration techniques can be simulated during the design phase, allowing the optimization of ADC performance even under process variations. The design flow can be used to extract information about sensitivity to operating and environmental conditions, post-calibration performance and also design yield, by extracting a database of Monte Carlo realizations of the ADC stages, so that it can be employed to optimize system and circuit design. Simulations using a 0.13-mu m CMOS technology show an accuracy of the model as high as 17 bits
Improved Digital Background Calibration of Time-Interleaved Pipeline A/D Converters
No full textWe propose an algorithm for the digital background calibration of time-interleaved analog-to-digital converters (ADCs), which is capable of accurately calibrating errors due to offset, gain, and timing mismatches, as well as nonlinearities due to errors in the channel ADCs. Calibration is performed in the background without interrupting data conversion, even in the presence of wideband input signals and signals beyond the first Nyquist band. The proposed algorithm improves a previous work by the authors by allowing higher precision, particularly in the case of many interleaved channels and large mismatches. Accuracy improves by 3-8 bits with respect to the previous algorithm and up to 10 bits with respect to the uncalibrated case
Efficient Digital Background Calibration of Time-Interleaved Pipeline Analog-to-Digital Converters
No full textA novel technique for the digital background calibration of time-interleaved analog-to-digital converters is proposed. The technique corrects at the same time for both errors due to gain, offset and timing mismatches among the time-interleaved channels and errors due to nonlinearities in the channels, for instance due to capacitor mismatches in switched capacitor implementations. This feature, together with the use of the recursive least mean squares algorithm, makes the technique particularly fast (12 bits of accuracy can be achieved after about 4000 samples for a two-channel converter). The proposed calibration technique employs wideband differentiators, thus enabling digital background calibration of timing skews even with wideband input signals. Besides, undersampled differentiator filters are proposed, and it is shown that the technique is capable of calibrating undersampling converters by estimating the derivative of wideband input signals even outside the first Nyquist band
Digital background calibration of subsampling time-interleaved ADCs
No full textA technique for the digital background calibration of subsampling time-interleaved analog-to-digital converters is proposed. The technique corrects the errors due to gain, offset and timing mismatches among the time-interleaved channels by estimating and nulling the errors with respect to a reference channel through least mean squares loops. Wideband undersampled differentiator filters are exploited thus enabling digital background calibration of timing skews even with wideband input signals outside the first Nyquist band
On the Feasibility of Cascode and Regulated Cascode Amplifier Stages in ULV Circuits Exploiting MOS Transistors in Deep Subthreshold Operation
Full text linkIn the last years several ultra-low voltage (ULV) operational transconductance amplifiers (OTAs) with supply voltages below 0.5V have been proposed in the literature. To achieve high gain, multi-stage amplifiers are frequently exploited, in spite of the complexity of design and compensation approaches, whereas cascode and regulated-cascode OTA topologies have rarely been exploited to implement ULV amplifiers. On the other hand, most ULV amplifiers are designed for IoT and biomedical applications in which reducing power consumption is the most important specification, and MOS devices are operated in the subthreshold region. This paper focuses on exploiting the subthreshold operating region to design ULV single-stage OTAs that utilize an output cascoded branch to increase the equivalent output resistance and, consequently, the overall voltage gain. A detailed analytical study of the conditions for triode and saturation regions for MOS devices operating in deep subthreshold region is presented to demonstrate that, for an appropriate choice of the inversion coefficient (IC), a cascode configuration exhibits higher gain than a single transistor, for the same voltage overhead, even in ULV conditions. More specifically, the results presented in this work demonstrate that 4 MOS devices (2 NMOS and 2 PMOS) can be reliably stacked to build a complementary cascode amplifier, even with a supply voltage as low as 0.4V. We also present a novel topology of regulated-cascode amplifier suitable to be operated with a supply voltage of 0.4V and a voltage gain approaching 100dB. Simulation results referring to a 180nm CMOS technology and including PVT and mismatch variations confirm state-of-the-art performances, as well as the good robustness of the proposed regulated-cascode ULV OTA
Calibrating sample and hold stages with pruned Volterra kernels
No full textSwitched capacitor sample and hold (SHA) stages in deep submicron technologies can achieve hundreds of mega samples per second of sampling frequency, but are affected by several nonlinear effects which reduce their signal-to-noise-and-distortion ratio (SNDR): CMOS switch non-idealities, amplifier nonlinearity, and incomplete settling. It is possible to model and correct distortions using Volterra kernels, which can be rather resource-consuming as the number of parameters to estimate rapid increases with the order and length of the kernels. In this reported work, it is shown that a switched capacitor SHA, simulated using the 45 nm process by STMicroelectronics, can be calibrated to achieve a 10-24 dB improvement in SNDR. Computational costs are kept low using a different lag value for each kernel, and iteratively pruning the elements of the Volterra kernels which affect linearity the least. A technique for estimation and out-of- sample validation is presented and robustness checks are performed. A performance gain of 8.5 dB can be achieved with as few as 17 correction parameters, while 21 coefficients are enough to gain 12.2 dB, and 36 to gain 18.4 dB
Design Solutions for Sample-and-Hold Circuits in CMOS Nanometer Technologies
No full textSolutions for the design of low-voltage sample-andhold (S/H) circuits in CMOS nanometer technologies are presented. As a design example, a 0.8-V supply S/H is designed and simulated using a 130-nm CMOS process. It dissipates 0.5 mW at dc and provides almost a rail-to-rail signal swing. When clocked at 40 MS/s and with a 1.4-VPP differential input signal, the simulated spurious-free dynamic range, signal-to-noise ratio, and total harmonic distortion are 57, 67, and −56 dB (9 equivalent bits), respectively, with low sensitivity to supply, temperature, process, and mismatch variations. The proposed solution employs a three-stage low-voltage amplifier without a tail current source in the differential pair and a switch topology, which combines clock voltage doubling and dummy switches
Biasing technique via bulk terminal for minimum supply CMOS amplifier
No full textA biasing technique for minimum supply CMOS amplifiers is proposed. The bulk terminals of the input transistors of a pseudodifferential amplifier are exploited in a switched-capacitor control loop to set the quiescent current. Simulations on a design powered with 0.7 V show that the performance obtained is comparable to that of a traditional differential pair supplied with 1 V
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