Electronics Sci Instr
Electronics Sci Instr PHYS 3610
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This 32 page Class Notes was uploaded by Ericka Ryan I on Monday October 26, 2015. The Class Notes belongs to PHYS 3610 at University of Utah taught by Staff in Fall. Since its upload, it has received 38 views. For similar materials see /class/230024/phys-3610-university-of-utah in Physics 2 at University of Utah.
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Date Created: 10/26/15
Electronics 1 lecture 24 Short Intro to Noise Analog to Digital Conversion FET summary Signal v 006 intrinsic noise 004 0 Thermal or Johnson noise temperature induced electron motion 03902 l M 0 Shot noise 0 Mr illl lllrl hrlrwilltrquotllwill ll random fluctuation in pnjunctions W H pickup noise 0 Interference noise 3903904 beat from a powerful AC power 0060 01 02 03 04 05 O TranSlent nOlse Time s switching of nearby circuit 0 Fluorescent noise fluorescent lighting 100120 Hz External Atmospheric static Industrial Extraterrestrial Solar noise Cosmic noise lnternal Johnson Noise Shot noise 1f noise atmospheric lt 30 MHz typically generates lower frequencies line of sight propagation for gt 30 MHz manmade 1 600 MHz all manner of circuits Sun below 20 MHz penetrates ionosphere interferes with radio random noise in current conducting devices difficult to counteract can be described statistically power proportional to bandwidth b think power per Af b spectral density function random noise averages to 0 normalized mean square 7 n T T anz2dz 0 Thermal or IIIIIIISIIII iSB has a normal amplitude distribution Probability of e M e instantaneous value of voltage exceedlng 2 0 I 0 Time has a flat power spectrum white noise noise power between 1 2 Hz same as 999 1k Hz gt Only limited by bandwidth limitation of circuit ll Thermal III IDIIIISIIII Noise BBSiSt I S Definition from CD Motchenbacher s book Low Noise Electronic System Design Wiley Interscience Thermal noise is caused by random thermally excited Vibrations of charge carriers in a conductor A simple resistor produces thermal noise ltv2gt 4kTRAf lti2gt 4kTAf 1kg 9 4nVAf k Boltzmann constant 1383 x 103923 VCK T Temperature ambient 4kT 166 x 10 3920 VC Thermal III IDIIIISIIII Noise BBSiSt I S IUD j 10quot quot W 1 00 1 1G mm mm resistance in HW H zh equivalent ma ae mitags an Figure 738 Th rmal noiSe voltage versus resistance Thermal 0I IDIIIISIIII Noise canacitors RC circuit noise independent of R vn2 kTC thermodynamic distribution of e39 on capacitor also called reset noise an kTC or kTCnoise 9 capacitance limits noise on image sensors CCD thermal noise formulae given here limited to f ltlt kTh 68 F 9 kTh 6x1012Hz 6THz MOSFET and Thermal Noise sz 39D Transconductance AIDS gm AVGS i3 4kT FgmAf v35 4kT Fglef F 9 excess noise factor occurs when carriers traverse a boundary between to media 9 semiconductorjunction lti2 gt 2eIAf shot with c charge of single electron l current Again total power proportional to bandwidth white noise power spectrum flat Bquot and SIIIII Noise transconductance g Aic m Avbe average noise power i3 41 gmAf vi 414 gm39lAf 1Itl iclterl Noise Related to conduction phenomena Negligible for conductors amp resistors 7 Weak for BJT strong for MOSFET constant in each decade lf noise Circuit bandwidth Thermal noise Signal frequency spectrum Circuit frequency response Noise F100 f limit your bandwidth for a circuit that is input to another circuit 9 investigate and define the equivalent noise source V or I GIII I BIIIS Tlll ll ll EN and leads can lead to unreliable wrong measurements Cause Pickup and GND currents offsets II long amp small diameter lead Solutions wires with relatively high resistance I temperature induced resistance 39 proper 33926 Of lead W39res on lead wires proper shielding of lead wires Lead wires located close to use of bandpass filter to block other electrical devices all but desired frequencies Lead wires enclose large area general adVIce separate logic and analog GND use shielding beware of ground loops Signal to Noise Ratio SNR luldgi cm Noise Figure MATH vi NP 1010gm 4km 7101quot 1 3539 dB 7 02m 4H 3 llealing Will noise oEliminate interference oDon t screw up grounding 7 7 A gt7quot A mm was Grounding Ill distant ciruils T iquotIJUl uulle 23quot 4 grid P39igun 77 Opm cm1pled analug ismlatinn mnp cr The Art of Electronics Horowitz and Hill Analog I0 lligital converters Successive Annroximation Am D7 1 mg nal L x mm 39 g is mm m an successwe appraximaliun regwstw 77 s sxar conv manual and or Q C ccnv Figure 951 Successiveapproximation ADC oFaster but not cheaper mnntnr n quotIH39 FIFE r uuu m Effquot V j L time F 39a39il39l39 VIPquot339 quot L T 93 4 atlr f II39r IE Singleh l pi xcuw39 quot Resolution and Ilvnamic ange Voltage range Vr Number of bits N Resolution VrZN Dynamic Range VrVrZN 2N No need to have minimum signal to be 10 x smaller than noise mamas ANALeGrmrmeHALwNVEmERs was x a 22 g I AWan m 3 as 5 m 475115 3w wan m 10 SA 3 AW 53 mama m mm mm was mmde P mam nmwm sA 5 m Nanormqu r 90 A swnove winW s Mu ymP wz an mm Wn zdssx mm m m I mm FE39I39 Summary JFET nr duplclmn 1quotISI III39 prclmnncl thnncunrnl ML ISFEI Hchunnu IH hunncl Enhanccmcnl VIIiJSf ifl p ch1lmcl f f 391 i V s s s 1 in f G of c 40 B G H o B I II J In 0 1 1 n D D l i V r I m 1m 39m 31FET a Enhancement h 39 h Depletion M051 Ll Mo l39bl I JFET bl Dcplcliun MOSFEI39 r Enlmmcnmul MOSFET nnnl BIT Collector Base Emitter 9 PET nchannell Source Gate Drain active 6 controlled by iB 9 i0 3iB vBE 07V or 08V or lto5v 9 saturation iG 0 ll controlled by VGSI depletion amp JFET iD IDss139VGsVp2 enhancement iD KVGS39Vt2 saturation vBE 08V iC lt BiB vCE 02V 9 ohmic VDs lt VGS Vp 2 iD IDSS2I P P P 39G 0 VDs lt VGSVt in K2VGS V1VDS V1325 cutoff vBElto5v 9 i0 iBO cutoff 9 pinchoff vGS s VIo ID U My IFE39I39 Summary n channel Triode or Ohmic region VGA VD EV iolw2Iv me VP gtgt VD8 9 b so vp Saturation or Active region G 9 VM v 2 05 quot V in UNAVWVP i 1 1 i D DSS VP in my I 0 e lt Tiiodc reginigt Salumnon region gt 5 I IK W m r depletion MOSFET JFET enhancement MOSFET m Triode or Ohmic region iD K2V55 VLVDS V025 2 mm again VDS ltlt1 39G O Saturation or Active region 9 in 2KVGS WVDS i0 VG K21 AVDS typically 001V391lt lt01V391 a r VDS z 1 D5 2KVo Vt simplified in KVGS v2 lD Midterm 4 Final Midterm 4 Tuesday Dec 9 JFET MOSFET OTA AM Modulation Final Exam Comprehensive Tuesday December 16 at 8301030 PM JFB 102
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