Search results for "Transistor"
showing 10 items of 234 documents
Liquid-phase alkali-doping of individual carbon nanotube field-effect transistors
2012
Hiilinanoputket ovat todella herkkiä niiden lähiympäristössä tapahtuville muutoksille, joten niiden virrankuljetusominaisuuksia pystytään suhteellisen helposti muokkaamaan. Aromaattiset molekyylit esimerkiksi vuorovaikuttavat hiilinanoputken kanssa pii-pii -vuorovaikutusten välityksellä, jolloin molekyylien ja hiilinanoputken välillä voi tapahtua varausten siirtoa. Varausten siirtyminen taas muuttaa hiilinanoputken Fermi-tasoa ja vaikuttaa putken virrankuljetusominaisuuksiin. Myös atomeja voidaan kiinnittää hiilinanoputken seinämiin esimerkiksi sähköstaattisten vuorovaikutusten avulla, jolloin varausten siirron ja Fermi-tason muutoksen myötä putken virrankuljetusominaisuudet muuttuvat. Näid…
Synthetic approach to the design of wide-band microwave injection-locked amplifiers
2010
In this work, a synthesis-based approach to the realization of wide-band microwave injection-locked amplifiers (ILA) is proposed. To this purpose, a transmission-type topology is combined with a feedback structure in which the "core ILA" is intentionally separated from the output (power) amplifier. A modular, matched, design of individual building blocks of the core ILA is then adopted, which allows their first-approximation exact modeling in the dynamical complex-envelope domain, following the theory earlier developed by Calandra-Sommariva. On this basis, analytic expressions for the main operating characteristics of the ILA (such as the locking bandwidth under small signal operation) are …
Approach to the Design of Transmission-Type Injection-Locked Microwave Oscillators through Behavioral Block Modeling
2010
In this work, an attempt is made toward the development of a systematic design method for the performance- driven dimensioning of the various elements comprising the structure of modern transistor-based microwave injection- locked oscillators with transmission-type topologies (TILOs). The proposed approach is based on the use of appropriate diakoptics of the various circuit blocks into a matched environment, and their behavioral modeling in the fundamental- frequency dynamical complex envelope domain with the help of standard circuit and E.M. simulation CAD tools. This will permit, in the end, to obtain closed-form expressions for the main TILO performances in terms of the design parameters…
Enhanced Thin-Film Transistor Performance by Combining 13,6-N-Sulfinylacetamidopentacene with Printed PEDOT:PSS Electrodes
2011
Bottom-contact/bottom-gate organic thin-film transistors (OTFTs) are fabricated using a soluble pentacene precursor (13,6-N-sulfinylacetamidopentacene; SAP) and inkjet printed PEDOT:PSS electrodes on bare SiO2 dielectrics. Saturation mobility, Ion/Ioff ratio, and threshold voltage parameters, respectively, of 0.27 cm2 V−1 s−1, 105, and −4.25 V were measured under ambient conditions after the thermal conversion of SAP to pentacene in 100 μm long channel OTFT devices. The results obtained by the above solution approach are comparable to that of vapor-phase grown pentacene-based OTFTs with photolithographic gold contacts and organic buffer layers and/or inorganic injection layers. The present …
Asymptotic theory of resonant tunneling in quantum waveguides of variable cross-section
2008
Halkaisijaltaan muunnellun kvanttiaaltojohtimen kapenemat toimivat tehokkaina potentiaalivalleina elektronin pitkittäissuuntaiselle liikkeelle. Kaksi kapenemaa muodostaa kvanttiresonaattorin, jossa resonoiva tunnelointi voi tapahtua. Tämä tarkoittaa sitä, että elektronit, joiden energia on lähellä resonanssia, läpäisevät resonaattorin todennäköisyydellä lähellä yhtä.Sarafanov kuvailee väitöskirjassaan asymptoottisesti elektroniaallon etenemistä kvanttiaaltojohtimessa, jossa on kaksi kapenemaa. Aaltoluvun k oletetaan olevan ensimmäisen ja toisen kynnysluvun välissä, jolloin vain sisään tuleva ja poismenevä aalto voivat edetä jokaisessa aaltojohtimen päässä äärettömyydessä. Väitöskirjassa esi…
Hiilinanoputkien käyttö transistorikomponenteissa : hiilinanoputkinäytteiden laadun parantaminen, transistorikomponenttien valmistus sekä niiden sähk…
2011
Puolijohdeteollisuuden kantavana voimana on alusta saakka ollut mikroprosessorien laskentatehon jatkuva kasvu, minkä on sallinut valmistusmenetelmien alituinen tehostuminen. Erityisen merkittävässä osassa on ollut yksittäisten transistorikomponenttien koon pienentyminen, sekä niiden pinta-alatiheyden kasvu substraatilla. On kuitenkin tunnustettu tosiasia, että sama kehitys ei voi jatkua enää pitkään, sillä jo nyt toimitaan nykyisten valmistusmenetelmien fysikaalisilla äärirajoilla. Suotuisan kehityksen turvaamiseksi on siis välttämätöntä ottaa käyttöön kokonaan uusia menetelmiä ja materiaaleja. Tutkielmani liittyy hiilinanoputkien (carbon nanotubes, CNTs) käyttöön sähköisissä komponenteissa…
Nanoporous kaolin – cellulose nanofibril composites for printed electronics
2017
Cellulose nano- and microfibrils (CNF/CMF) grades vary significantly based on the raw materials and process treatments used. In this study four different CNF/CMF grades were combined with kaolin clay pigment particles to form nanoporous composites. The attained composite properties like porosity, surface smoothness, mechanical properties and density properties depended strongly on the raw materials used. In general, higher kaolin content (~80 wt%) led to controllable shrinkage during drying, which resulted in improved dimensional stability of composites, compared to a lower kaolin content (~50 wt%). On the other hand, the use of a plasticizer and a high amount of CNF/CMF was essential to pr…
A delay model valid in all the regions of operation of the MOS transistor for the energy-efficient design of MCML gates
2013
This paper presents a novel delay model for MCML circuits valid in all the regions of operation of the MOS transistor, i.e., weak inversion (sub-threshold), moderate inversion (near-threshold) and strong inversion. The proposed delay model was employed to develop an automated methodology for the energy-efficient design of such circuits. The tradeoff that can be realized between energy and delay was investigated. Experiments were performed using different technologies to understand the impact of technology scaling on that tradeoff too. Major results of this study are as follows. In a circuit designed for minimum energy consumption, the minimum energy point occurs in the near-threshold region…
Employing Microwave Graphene Field Effect Transistors for Infrared Radiation Detection
2018
In this work, we investigate the possibility of employing graphene field effect transistors, specifically designed for microwave applications, as infrared detectors for telecom applications. Our devices have been fabricated on a sapphire substrate employing CVD-grown transferred graphene. The roles of both the gate dielectric and the DC bias conditions have been evaluated in order to maximize the infrared generated signal through an experimental investigation of the signal-to-noise ratio dependence on the transistor operating point.
Benefits and Drawbacks of A High Frequency Gan Zvzcps Converter
2017
This paper presents the benefits and drawbacks of replacing the traditional Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching (ZVZCPS) converter. This type of converters is usually used as Electronic Power Converters (EPC) for telecommunication satellites travelling-wave tube amplifiers (TWTAs). In this study, firstly the converter is theoretically analysed, obtaining its operation, losses and efficiency equations. From these equations, optimizations maps based on the main system parameters are obtained. These optimization maps are the key to quantify the potential benefits of GaN transistors in this type of…