Researcher: Mahmutoğlu, Ahmet Gökçen
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Mahmutoğlu, Ahmet Gökçen
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Publication Metadata only Non-monte carlo analysis of low-frequency noise: exposition of intricate nonstationary behavior and comparison with legacy models(IEEE-Inst Electrical Electronics Engineers Inc, 2016) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756Modeling and analysis of low-frequency noise, such as 1/f and burst noise, with time-varying bias conditions is a long-standing open problem in circuit simulation. In this paper, we offer a solution for this problem and present a computational model for low-frequency noise. The merits of our model are twofold. First, it is fully nonstationary. It can represent noise processes with time-varying statistics that are tightly coupled to the circuit variables in a stochastically correct manner. Second, its mathematical structure allows the utilization of well-established, non-Monte Carlo noise analysis techniques which are orders of magnitude faster than their Monte Carlo counterparts. We first provide an overview of our noise model along with the legacy modeling techniques. We verify that, when used with fast non-Monte Carlo analysis methods, our noise model produces results with the same accuracy as computationally laborious Monte Carlo simulations. We then proceed to contrast our nonstationary noise model with the legacy modulated stationary model. As a typical instance, where the results produced by these two models differ significantly due to intricate nonstationary behavior, we analyze the switched biasing technique that was proposed in order to reduce low-frequency noise. As a case study, we examine the 1/f noise behavior in the previously proposed coupled sawtooth oscillator circuit and show that, whereas simulations conducted with the legacy modulated stationary model suggest that no noise reduction is obtainable with switched biasing, our nonstationary noise model predicts the correct amount of noise reduction observed in previously published experimental data.Publication Metadata only Modeling and analysis of nonstationary low-frequency noise in circuit simulators: enabling non Monte Carlo techniques(IEEE-Inst Electrical Electronics Engineers Inc, 2015) Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Demir, Alper; Mahmutoğlu, Ahmet Gökçen; Faculty Member; PhD Student; College of Engineering; Graduate School of Sciences and Engineering; 3756; N/AModeling and analysis of low frequency noise in circuit simulators with time-varying bias conditions is a long-standing open problem. In this paper, we offer a definite solution for this problem and present a model for low-frequency noise that captures the internal, stochastic dynamics of the individual noise sources via dedicated internal pseudo nodes that are coupled with the rest of the circuit. Our method correctly incorporates the inherent nonstationarity of low-frequency noise into the device model and the circuit simulator. It is based on a probabilistic description of oxide traps in nano-scale devices that individually cause the so-called random telegraph signal (RTS) noise, and, en masse, are believed to be the culprits of other low-frequency noise phenomena, such as 1/f and burst noise. Our model captures the dependence of noise characteristics on the state variables of the circuit. Its simple yet precise mathematical formulation allows the utilization of well-established, non Monte Carlo techniques for nonstationary noise analysis. In one embodiment that we present in this paper, the proposed noise model is used to perform frequency-domain, non Monte Carlo, semi-analytical noise evaluation for circuits under periodic large-signal excitations. For this case, we verify that the computed noise spectral densities match the ones obtained via spectral estimation from timedomain Monte Carlo noise simulation data. © 2014 IEEE.Publication Metadata only Modeling and analysis of (nonstationary) low frequency noise in nano devices: a synergistic approach based on stochastic chemical kinetics(Institute of Electrical and Electronics Engineers (IEEE), 2013) Roychowdhury, Jaijeet; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756Defects or traps in semiconductors and nano devices that randomly capture and emit charge carriers result in low-frequency noise, such as burst and 1/f noise, that are great concerns in the design of both analog and digital circuits. The capture and emission rates of these traps are functions of the time-varying voltages across the device, resulting in nonstationary noise characteristics. Modeling of low-frequency, nonstationary noise in circuit simulators is a longstanding open problem. It has been realized that the low frequency noise models in circuit simulators were the culprits that produced erroneous noise performance results for circuits under strongly time-varying bias conditions. In this paper, we first identify an almost perfect analogy between trap noise in nano devices and the so-called ion channel noise in biological nerve cells, and propose a new approach to modeling and analysis of low-frequency noise that is founded on this connection. We derive two fully nonstationary models for traps, a fine-grained Markov chain model based on recent previous work and a completely novel coarse-grained Langevin model based on similar models for ion channels in neurons. The nonstationary trap models we derive subsume and unify all of the work that has been done recently in the device modeling and circuit design literature on modeling nonstationary trap noise. We also describe joint noise analysis paradigms for a nonlinear circuit and a number of traps. We have implemented the proposed techniques in a Matlab ® based circuit simulator, by expanding the industry standard compact MOSFET model PSP to include a nonstationary description of oxide traps. We present results obtained by this extended model and the proposed simulation techniques for the low frequency noise characterization of a common source amplifier and the phase jitter of a ring oscillator.Publication Metadata only Modeling and analysis of nonstationary low-frequency noise in circuit simulators: Enabling non Monte Carlo techniques(Ieee, 2014) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756Modeling and analysis of low frequency noise in circuit simulators with time-varying bias conditions is a long-standing open problem. In this paper, we offer a definite solution for this problem and present a model for low-frequency noise that captures the internal, stochastic dynamics of the individual noise sources via dedicated internal pseudo nodes that are coupled with the rest of the circuit. Our method correctly incorporates the inherent nonstationarity of low-frequency noise into the device model and the circuit simulator. It is based on a probabilistic description of oxide traps in nano-scale devices that individually cause the so-called random telegraph signal (RTS) noise, and, en masse, are believed to be the culprits of other low-frequency noise phenomena, such as 1/f and burst noise. Our model captures the dependence of noise characteristics on the state variables of the circuit. Its simple yet precise mathematical formulation allows the utilization of well-established, non Monte Carlo techniques for nonstationary noise analysis. In one embodiment that we present in this paper, the proposed noise model is used to perform frequency-domain, non Monte Carlo, semi-analytical noise evaluation for circuits under periodic large-signal excitations. For this case, we verify that the computed noise spectral densities match the ones obtained via spectral estimation from time-domain Monte Carlo noise simulation data.Publication Metadata only Modeling and simulation of low-frequency noise in nano devices: stochastically correct and carefully crafted numerical techniques(IEEE-Inst Electrical Electronics Engineers Inc, 2015) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756Defects or traps in semiconductors and nano devices that randomly capture and emit charge carriers result in low-frequency noise, such as burst and 1/f noise, which are important concerns in the design of both analog and digital circuits. The capture and emission rates of these traps are functions of the time-varying voltages across the device, resulting in nonstationary noise characteristics. Modeling of low-frequency, nonstationary noise in circuit simulators is a long-standing open problem. It has been realized that the low-frequency noise models in circuit simulators were the culprits that produced erroneous noise performance results for circuits under strongly time-varying bias conditions. In this paper, we present two fully nonstationary models for traps, a fine-grained Markov chain model and a coarse-grained Langevin model based on similar models for ion channels in neurons. The nonstationary trap models we present subsume and unify all of the work that has been done recently in the device modeling and circuit design literature on modeling nonstationary trap noise. We provide a detailed explication of these models with regard to their stochastic properties and develop carefully crafted circuit simulation techniques that are stochastically correct. We have implemented the proposed techniques in a MATLAB-based circuit simulator, by expanding the industry standard compact MOSFET model PSP to include a nonstationary description of oxide traps. We present results obtained by this extended model and the proposed simulation techniques for the low-frequency noise characterization of a common source amplifier and the phase jitter of a ring oscillator.Publication Metadata only CIRSIUM: a circuit simulator in MATLAB® with object oriented design(Institute of Electrical and Electronics Engineers (IEEE), 2013) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756We present CIRSIUM, a CIRcuit SImulator Using MATLAB ® and its object oriented programming language. CIRSIUM has been developed as a flexible and modular framework in order to enable the rapid development of new device models and prototyping of new circuit analysis paradigms and algorithms. The modular core code includes the PSP MOSFET compact model and uses SUNDIALS for the solution of dynamical circuit equations. New device models can be added by supplying their stamps in vector/matrix form, and existing models can be translated from the Verilog-A hardware description language using ADMS that automatically computes the necessary Jacobians. CIRSIUM has been initially developed for the analysis of random telegraph signal (RTS) noise in nano-scale integrated circuits. For this purpose, the PSP MOSFET compact model has been expanded with a detailed, non-stationary RTS noise model, that includes a physical description of gate oxide defects and the calculation of their voltage and position dependent capture/emission time constants. Future applications of CIRSIUM will include non-electronic systems, such as noise modeling and analysis for biological neurons, neuronal networks and the nervous system.Publication Metadata only Analysis of low-frequency noise in switched MOSFET circuits: revisited and clarified(IEEE-inst Electrical Electronics Engineers inc, 2015) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Mahmutoğlu, Ahmet Gökçen; Demir, Alper; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 3756Traps that are located in the gate oxide of MOSFETs have been established as a cause of low-frequency noise phenomena. analysis of such noise is usually based on frequency domain, stationary models. It has been shown that such simplistic models produce erroneous results for circuits with time-varying bias conditions. Tian et al. proposed an idealized trap model with the goal of capturing the nonstationary behavior of oxide traps, and were able to elucidate the experimentally observed large noise power reduction in switched MOSFET circuits which eluded any explanation obtainable with legacy stationary models. in this paper, we build on their seminal work and first identify an oversight in their model derivation which had produced an incorrect expression for the single trap noise spectrum. We next derive the correct spectrum expression, verify it against detailed idealized trap simulations and discuss its implications. the idealized trap model is amenable to analytical derivations and useful as a first stage in understanding nonstationary trap noise. We then demonstrate that noise simulations based on a detailed trap description implemented in a compact MOSFET model in a circuit simulator are needed for an accurate characterization of low-frequency noise in switched MOSFET circuits that matches experimental results.