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NATIONAL M D I O SCIENCE CONFERENCEFeb. 24-26,1998 Helwan Cairo ,Egypt,

A El-Hennawj *, E Y ousry **, A Ramadan**>H Abd El-hanieed"", NI abd El-Fatah**AmShams Uruversity-Fac Of Erig -Dept -oi'Electronics**H@er Technological Lnslttute-Dept orElectronics and Computer, 10"' of RariiadanciQAbstract - Many ~nstrumentsand devices are in use and satisfying performancerequirements. However, most are neither cost effective nor reliable They are bulky, heavy andsophisticated Moreover, they can't be integrated using MOSFE'T technology on single chipThe paper presents a new detector for precise detection of microwave signals The new detectoris constructed of a short channel MOSFET (L -2pm1, acting as a hot carrier injector,surrounded by four diffused collectors, which are topologically, arranged so as to detect themagnitude of the magnetic field to be measured or monitored and determine its orientation Acurrent cross-coupling technique is used to compensate for the sensor leakage currents (60dBsmaller) A negative feedback IS introduced to improve the detector linearity (better than 2%)and stabil ity Magnetic field as sinal1as 10nT have been measured ovei a wide dynamic range(-120 dB) of measurement

A gre,zt attention has been, recently given to the development and realization of preciseMOSFET IC microwave signals detector This is relei red to the remarkable advances in the deviceconcepts and technology and because precision microwave signals detector found wide fields ofapplication qlthough, a variety of seimconductor microwave signals detector have beeninvestigated, the new device proposed in this paper has not introduced before The constructionand operation of which as shown in Figs (1) and (2) isbased on lateral injection of carriers from acentral inj ectx into four diffused collectors which are topologically arrangedso as to detect themagnitude arid direction of the magnetic field component of the electromagnetic wave to bemeasured or monitored It i s entirely integrated using the standard2pm, single-gate monochannelMOSFET Technology It employs two leakage compensation techniques one with the sensor andthe second with the detector Lt is quite simple, easy to construct and realize and compatible withthe MOSFET scalingdown trends It is idso provided by supplementary circuitries to performautomatic scale changement Detailed analysis and experimental characterization of the presentdevice is given - sections 2 and 3 - where the device construction is investigated with adescription of its mechanism of operation

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NATIONAL RAD1 SCIENCE C Q NFE m NC E98,Helwan ,Cairo Egypt.

2.3Response 1J pgradingThe opmtion proposed microwave sensor, as shown from the above discussion, is basedon direct propagation of electrons from the central source to the surrounding collectors. Thispropss is limited only by the propagation delay which is shorter than 20 p sec (L=2pmand V -10 cdsec) Such delay never limits the response to microwave signalsThe circuitries used to process the sensor output is operated in the ultra low powerexponential region o f operation [3] In this region MQSFET current can grow up from 10pA to

0 1 mA abruptly with a very short delay (about 10sec )which allows the detector to respond tothe microwave signalsMoreover the circuit configuration of Fig(3) is actually replaced by cascade connectedMOSFET's which reject the M il ler effect and greatly push up the detector speed of operation

2.4- L eakage-Currents CompensationThere are two main leakage components, the first is created within the sensor and is relatedto the collector-junction leakage arid to the device proximity currents [2,3,5].The second iscreated within the detector and i s I elated to the switches and capacitor leakage currents Theseleakage components limit the detector sensitivity, reduce the dynamic range of measurement anddegrade its resolutionThe f i rst component is compensated using the current cross-coupling technique shown in

Fig.(3) In which the voltage signal 6V of a certain collector ( the sourceof T, ) s created due tomagnetic currI2nt +61together with the branch leakage current I,,while6V' of the other collector (the source of TJ ') is created due to magnetic current- 61together with a leakage current ][',whichequals to I,,

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NATIONAI , RADIO SCIE NCE CONFEK ENCEFeb. 2426,1998,Helwan ,Cairo,Egypt.

3- PFUNCIPLE OF OPERATION AND MODELINGUnderstanding of the device operation needs good knowledge of carrier substrate current

3.1- Hot Carr ier Substrate Current GenerationThis current results from the carrier heating occurring in MOSFET channel. I t is sensitiveto the biasing voltage and device geometry It is also dependent on the surface doping profi le

~ 4 1When a large channel electric field E, is applied, some of tbe primary electrons gainenough energy and exercise collisions with the lattice causing impact ionization and creatingtherefore new electron-hole pairs The secondary electrons are collected by the positively biased

drain The secondary holes are injected into the channel depletion region (as shown in Fig(4)), bythe action source-substrate junction potential and the substrate biasVBand are collected by thesubstrate to constitute the substrate currentk3.2- Formulating and modeling

Straight forward treatment of Eq's (1-a>and (1-b) shows that the exponentialcurrents(I expi,1 ) can be formed by [2,4]

-8 - 2 4Where k', k and a are constants respectively equal to 10,3x10 and 10 I is the source fimctionreverse current (- 10PA).The currents Iespl, 1 are converted again into voltages, and these voltages are compared andamplified using the circuit configuration shown in fig (9,

taking R I R sand R z so as to make R R dR2= 10,8and adjusting the injection biasing conditionsothat B =lo,g=3000cm2/ V.sec and IFO. 1 pA, then,= 10. 8. 10- L. B, ( 4 - b )

If v is allowed to vary from 1mv to 2v ,then &,cmbe measured within a dynamic range extendingfrom 10mT up to 20T

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AT IONAL RADIO SCIE NCE CONFERENCEFeb. 2426,1998,Helwan ,Cairo, Egypt.

This technique isonly suitable for high level field measurements sirice it allows a narrow dynamicrange of measirrements but it compensates further all leakage and parasitics. Scale changement isallowed via vaiiation of K, and/or4. owever alternative technique allowing wider dynamic isrequired3.3- Wide Range Detector

Figure (6) shows the block diagram of this alternative technique which fulfi lls twoservices; a) en1argement of the dynamic range of measurement and pronouncely improving theresolution and b) compensate further all leakage currents and parasitics caused due to the devicemismatching and offset voltage in this stageIn this technique two current to frequency converters CFCl and CFC2 are used to convert

the exponential currents Zexp l , exp2 into propoitional frequencies VI andF, [2,3,5]

A third one CFC3 which is only sensitive to leakage current and parasitics. Therefore, the outputfrequency E js proportional LO these leakage and parasitics and their excursion with ambienttemperature,1

C.AVF 3 2 --1 I L ( 5 - c )This frequency 5 is used to monitor the two MOSFET 7; and T2and forces them to sink a currentI from each of the inputs of CFCl and CFC2. This action modifies7 and F2and makes themleakage free Combining Eq's (2) and ( 5 ) yields,

3 YF 1 10 . I 3 F 7 10 .E3For F to vary ffom 1Hzto 10ME-lz, magnetic field excursion as small as 1nT can be detected overa dynamic range of operation extending from 1nT up to ImT with a better than 2% linearity ofresponse.

4- EXPERIMENTAL A ND SIMULATION RESULTSThe test specimens are realized and supplied by the French - society Thomson EFCIS.HMOs I and 11technologies are used The measurements are achieved as follows Magnetic fieldsranging from 1nT to 0.01'r are applied and the corresponding CFC output frequencies aremeasured with and without compensation Magnetic fields in the same range (1nT to 001T) itrereplaced by equivalent proportional currents which are fed to the CFC active loop input while nocurrent is fed to the input of the CFC compensation loop

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NATIONAL RADIO SCIE NCE CONFERENCEFeb. 24-26,1998, Helwan ,Cairo, Egypt.

Figures (7) and (8) show the experimental F/B transfer characteristics of the Sb -MOSFET microwave signal detector with and with compensation We notice that, thecompensation allows to decrease the value of the smallest measurable magnetic field B to 10 nTat a very good linearity (better than2 percent) and excellent resolution (1 ppm) over avery widedynamic range ( 106 A) Moreover this detector provides a powerhl solution to a seriousproblem which has received continuous challenge and given great effort during the lasttenyears This problem of inability todetermine the direction of the magnetic field in all the existingdetectors They are only capable of detecting the no detection is performed and no alarm is8' enThe original sensor configuration used with this detector enableus to give a 360' polar indicationof the B directions When no compeqsation is inserted, the smallest tneasurable magnetic field israised to about 5x0 1 pT and minimum output frequency to nearly 10Hz

5- CONCLUSIONA novel substrate hot-carrier based microwave signal detector inH MO s technology has beeninvestigated It employs new techniques to compensate for the sensor and detector leakagecurrents and ensure that the detector has a linear response to the magnetic field B to be measuredAn analytical modeling was presented, and verified by experimental examination andcharacterization of the device The device is seen to have a very high sensitivi ty (10Hz / MT ) ,avery good linearity (better than 2 % ) ,avery wide dynamic range of measurement (10 nT to0 01 T) , excellent resolution , a capability to give a 360 polar indication of B direction ,and asensitivity enhancement without need to scale down the device geometry

REFERENCES[ I ] L, TISTIC , T SHY , PI BALTES, "A Lateral M agneto Transistor Structure With a L inearResponse to M agnetic F ield " IEEE Tran Elec Dev ,Vol 36, No 26, pp 1076 -1989[2] A EL-HENNAWY and F AL-MARZOUKI, ('Study And Characterizatlon Of M OSFET ICMagnetodetector Based On Hot Carrier Injection " IEE Proc C Vol 139, No 21, pp 119- 125,1992[3]A EL - "NA WY and M ABDEL-FATTAH, A RAMADAV and H ABDEL-HAMEED."Design and Investigation of a Very Wide Dynamic M icrowave Electronic Counter EntirelyIntegrated Using Traditional MOSFET Technology ( - IE4 Hz TO 1El1Hz ) " 4fh nt IEEEECS conf, Cairo EGY PT 1997

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NTH NATIONAL I U D 1 0 SCIENCE CONFERENCEFeb. 24-26, 1998 Helwan ,Cairo, Egypt.

[4] A E L 4 ENNAWY, G AL- BARAKATl and T AL-FLAIIBI, ''Study Arid InvestigationOf the Threshold Voltage Instability Caused By 'The HC Substrate Current" ,Itit JElect ,VoI N O I , PP 49-55, I093[S I A EL-HENNAWY M EL-SAEED, E YOIJSRY, A RAMADAN " Study andrealization of a New MOSFET FIigIi Precision Viscometer L 10" I nt ICM conf ,Cairo.EGYPT 1996

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1-1NATIONAL RADIO SCIENCE CONFEIUNCE mlFeb. 24-26 ,1995,Hellwan ,Cairo ,Egypt.

i ' ig ( 5 ) Circui t coi l f igurat ion orcurreiik to vol~ageonversionni id aiiiplificatiotl.