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Compensation method for multistage opamps with high capacitive load using negative capacitance
, Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 63, Issue 10 , 2016 , Pages 919-923 ; 15497747 (ISSN) ; Sharif Bakhtiar, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
It is shown that negative capacitance (NC) circuits can be systematically used to improve the gain-bandwidth product of the operational amplifiers (opamps). The NC circuit moves the nondominant pole of the opamp to higher frequency by decreasing the parasitic capacitance of the critical node. The impedance at the input of the NC circuits is neither purely capacitive nor negative at all frequencies. A design guide is presented by deriving the circuit model for a conventional NC circuit and investigating the extent of the improvement that can be achieved in a circuit by the use of the NC circuit. The model is then used to present the design guide for widebanding the multistage opamps with...
Design of Oscillator with Active Inductor and Investigation of Noise Cancellation in Oscillators
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
In this thesis, at first, we study the active inductors have been reported in the literature. Then by choosing one of them and investigating its advantages and disadvantages, we changed the structure in a way to solve its problems. On the way by using this active inductor and a negative capacitor, we designed an oscillator in 1.5 GHz frequency that has -106 dBc/Hz phase noise at 1MHz offset and its FOM value is 160 dBc. Also this oscillator is capable of frequency tunability of oscillation from 500 MHz to 2.2 GHz. In this spectrum the phase noise is changing between -100 dBc/Hz and -110 dBc/Hz. In the second part, in the aim of improvement of phase noise of oscillator structures based on...
Investigation of the Ion Migration Mechanism and its Effect on the Slow Response of Perovskite Solar Cells
, Ph.D. Dissertation Sharif University of Technology ; Taghavinia, Nima (Supervisor) ; Mohammadpour, Raheleh (Supervisor)
Abstract
In recent years, organo-metal perovskite solar cells have attracted remarkable attention due to their low cost manufacturing method as well as the rapid growth of efficiency. Despite the fast growing efficiency of organo-metal perovskite solar cells, there are big challenges around their low stability under real operational condition. In addition to extrinsic parameters like oxygen and humidity, intrinsic instability of perovskite rises mainly from ion migration in perovskite film. In order to understand the ion migration and its effect on photovoltaic parameters of the devices, appropriate characterizations and analysis are needed. Since ions are much slower compare to electrons, their...
Design of Wide-Band, Low Noise, Low Power OPAMP using Negative Capacitance Circuit and a Novel Method for Reducing Power Consumption and Die Area of Active RC Filters
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
Gain bandwidth products of Operational Amplifiers are dependent to power consumption. In this thesis we introduce negative capacitance circuit as a candidate to improve GBWs of OPAMPs in constant power, or achieve the requested GBW in lower power consumption. First we characterize negative capacitance circuit and introduce a model for that. Then we see how pole-zero placement will change, when we add negative capacitance circuit to a circuit node. As an application we use this circuit in Folded Cascode and Current mirror OPAMPs and give design guideline for this topologies. A three stages and a one stage OPAMP is designed in 0.18um CMOS, for the application of negative capacitance...