• VacuumTubes,BJTorFET?• CircuitAnalysis:Amplifier&Feedback• ClassicBJTCircuits• ArduinoIntro

6.101 Spring 2018 Lecture 5 1

Acnowledgements: Yanni Coroneos, Neamen, Donald: Microelectronics Circuit Analysis and Design, 3rd Edition

VacuumTubes

•  NYTimes–  “Guitarheroesfavorvacuumtubeamplifiersintheirinstruments”

–  “Manyrecordingengineerstendtousevacuum-tubeequipmentintheirstudios”

–  “Somelistenerspaythousandsofdollarsforhigh-endtube-basedstereosystemsandCDplayers.”

6.101 Spring 2018 Lecture 5 2

Linear without feedback Characteristics independent of temperature Wider dynamic range

BJTorFET

•  Dependsonapplication•  Amplifiers

–  BJT•  aremorelinearthatMOSFET,betterfidelity(lowharmonicdistortion)

•  candrivelowimpedancesathigherpower•  lowernoisewithlowsourceimpedance

– MOSFET•  highinputimpedance•  Voltagecontrolleddevice=>lowerpower

6.101 Spring 2018 Lecture 5 3

TransistorConfigurations

6.101 Spring 2018 Lecture 5 4

+15V

+

Vin

-

+

VOUT

-

RL

R1

+

+

R2

[a] Common Emitter Amplifier [b] Common Collector [Emitter Follower] Amplifier

RE RE

+15V

+Vin

-

+

VOUT

-

RL

R1

+

+

R2

+

[c] Common Base Amplifier

TRANSISTOR AMPLIFIER CONFIGURATIONS

R2

+15V

R 1

+

Vin

-

+VOUT

-

RE

+

+

high input impedance, for general amplification

voltage gain = 1 ; use in amplifier output stage.

low input impedance for low impedance sources, for high frequency response.

BJT

FET

Common source Common drain [Source follower] Common gate

MillerEffect*–CommonEmitter

6.101 Spring 2018 Lecture 3 5

)](1[ LCmM RRgCC += µ

* Agarwal & Lang Foundations of Analog & Digital Electronics Circuits p 861

InputImpedanceandFrequencyResponse

6.101 Spring 2018 6

RV1 V2C

Av =V2V1=

j XCR+ j XC

=

1jωC

R+ 1jωC

=1

jωRC +1

Av =1

sRC +1

High frequency cutoff fhi =1

2πRC

log f

AV (dB)

-3dB

fHI or f-3dB

slope = -6 dB / octaveslope = -20 dB / decade

0

log f

Degrees

-45o

fHI or f-3dB

0o

-90o

PHASE LAG

Lecture 2

log scale

LowFrequencyHybrid-πEquationChart

6.101 Spring 2018 Lecture 5 7

High gain, better high frequency response Low input resistance

Unity gain, low output resistance High input resist.

High gain applications Moderate input resistance High output resistance

CascodeAmplifer

•  Twotransistoramplifer:commonemitter(CE)withacommonbase

•  MillereffectavoidedbysettinggainofCEstagelow.

•  CEstageprovideshighinputimpedance

•  Commonbase(CB)providesgainwithoutMillereffect;baseisgrounded.

6.101 Spring 2018 Lecture 5 8

Miller effect

No Miller effect

Objectives

•  PerformananalysisintothebehaviorofacomplicatedcircuitusingbasicpropertiesofBJT’s(npn,pnp)

•  Calculategainofthesystem

•  Discusscrossoverdistortionissuesinpush-pullamplifiers

•  Understandfeedback

6.101 Spring 2018 Lecture 5 9

ThreeStage–PushPullAmplifier

6.101 Spring 2018 Lecture 5 10

6.101 Spring 2018 Lecture 5 11

ThreeStageAmplifer–BlockDiagram

Feedback

Q3-Q4PushPull

6.101 Spring 2018 Lecture 5 12

•  Q3:EmitterFollower(positvecycle)

•  Q4:EmitterFollower(negativecycle)

•  Overallgain~1

•  Q3&Q4Vbearealwaysonediodedrop

•  Crossoverdistortion

aboutzerocrossing

CrossoverDistortion

6.101 Spring 2018 Lecture 5 13

Q2–HighGainStage

6.101 Spring 2018 Lecture 5 14

•  Sincelaststageisanemitterfollower,noden4shouldbebiasednearzerovolts.

•  Q2isacommonemitter

configurationwithapnptransistor.

•  Forpnpconfiguration,reversethepolarityofthevoltagesfromanpn.

mvVVI

g

rg

THTH

CQm

m

26

0

==

= πβ

Lm

m

o

Lov Rg

g

RA −=

−=

ββ

5701015

*38

4 −==

==

vCQ

CQTH

CQm

AI

IVI

g

Q1Analysis

6.101 Spring 2018 Lecture 5 15

Biasing

6.101 Spring 2018 Lecture 5 16

Biasing–QuiescentPoint

•  Determinethequiescentpoint•  ForBJT

–  assumeVbe=0.6V–  assumebasecurrentneglible

•  ApplyKVL,KCL

6.101 Spring 2018 Lecture 5 17

Biasing–QuiescentPoint

6.101 Spring 2018 Lecture 5 18

v(n5) = Vout = 0

v(n1) - v(n3) = 0.6

v(n2) = 15 – 0.6

0.6 ma

knv

knv

iiKCL rt

10)3(06.0

1)15()3(6.0:

−+=

−−

+=

vnvornv 4.12)1(13)3( −=−=

kkforvnv 3/303.12)1( −=

it

if

+ 0.6 -

-13.0

-12.4

KeyObservations

6.101 Spring 2018 Lecture 5 19

•  Crossoverdistortioncausedbybaseemittervoltage.

•  Feedbackresultsinoverallgainindependentofβ

•  Biasingnotprecise,highlydependentonsupplyvoltage(poorsupplyvoltagerejection)

ClassicBJTCircuits/components

•  DarlingtonPair•  Matchedtransistors•  Shortcircuitprotection•  Currrentmirror•  Schottkydiode•  BakerClamp•  Vbemultiplier

6.101 Spring 2018 Lecture 5 20

MPSA13Darlington

6.101 Spring 2018 Lecture 5 21

MatchedPair

•  Closeelectricalandthermalcharacteristics

•  Supermatchedpairsalsoavailable

•  Usedindifferentalamplifiersandmeasurementequipment

6.101 Spring 2018 Lecture 5 22

SuperMatchedPair

•  Characteristicsapproachtheoreticaltransistor

•  Vbematchedto50µv

•  hFEmatchedto2%

6.101 Spring 2018 Lecture 5 23

7805RegulatorShortCircuitProtection

6.101 Spring 2018 Lecture 5 24

•  WhenvoltageacrossR16exceeds~0.6volt,Q14divertsawaybasedrivetoQ15.

•  NoteDarlingtonpair

Q15,Q16

6.101 Spring 2018 Lecture 5 25

356Op-AmpShortCircuitProtection CurrentMirror

6.101 Spring 2018 Lecture 5 26

Schottky*Diode

•  Schottkydiodeformedwithmetal-semiconductorjunctionvspnjunction

•  Lowerforwardvoltagedrop:0.15-0.45vs0.6-0.7forpnjunction

•  Almostzeroreverserecoverytimes.

•  Usedin74LSserieslogicLow-powerSchottky

6.101 Spring 2018 Lecture 5 27

* Walter Schottky

Baker*Clamps

•  Reducesturnofftimebylimitingsaturation

•  BakerCampwithdiodes

•  BakerclampwithSchottkydiode

6.101 Spring 2018 Lecture 5 28

*named by Richard Baker (1956); drawings from http://en.wikipedia.org/wiki/Baker_clamp

VbeMultipler

6.101 Spring 2018 Lecture 5 29

BEVRRRV2

21 )( +=

Arduino

•  Lowcostopensourcemicrocontrolleranddevelopmentsystem–  16MHzATmega328,32KBflash,1KBEEPROM,2KBSRAM–  22I/Oports:analog/digital–  5V(19ma)operation

•  Idealforprototyping,processcontrollerorstatemachines

•  Maybeusefulforfinalprojectbutonlyinasecondary

manner:–  datadisplay,controllogic

•  Manyvariants:Uno,Nano,Pro,Teensy….

•  Originalsvsclones

6.101 Spring 2018 Lecture 5 30

ArduinoNano

6.101 Spring 2018 Lecture 5 31

SPI: +5, GND, MISO, MOSI, SCK

USB: programming & +5V power

reset

LEDs: Power, LED, Rx, Tx

ATMEGA 328P CPU

J1 – pin 1

J2 – pin 1 7-12 VDC in

J2 – pin 14 3.3V @20ma

J2 – pin 4 5V in or out

ArduinoNano

6.101 Spring 2018 Lecture 5 32

LM1115 5V

CH340 FTDI Clone 3.3V regulator

J2 – pin 1

J1 – pin 1

D3, D5, D6, D9, D10, and D11 provide 8-bit PWM output with analogWrite() D10 (SS), D11 (MOSI), D12 (MISO), D13 (SCK) same as SPI header

A0-A7 10-bit analog inputs referenced to 5V or AREF using the analogReference() function; A4 (SDA) and A5 (SCL) support I2C

A0-A7 10-bit analog inputs referenced to 5V or AREF using the analogReference() function.

MultifunctionI/OPinsPartialList

Pin Function1 Function2 Function3

D13 digitalI/O SCK(SPI) Built-inLED

D12 digitalI/O MISO

D11 digitalI/O MOSI

D3,5,6,9,10,11 digitalI/O PWM

D3 digitalI/O Interrupt1

D2 digitalI/O Interrupt0

D1 digitalI/O Tx

D0 digitalI/O Rx

A5 analogin SCL

A4 analogin SDA

6.101 Spring 2018 Lecture 5 33

SerialInterface

•  ArduinoNanocloneusesCH340G;needtoinstallserialportdriver.•  Driversonhttp://web.mit.edu/6.101/www/s2018/drivers/havebeen

tested.–  CH341SER_MAC:OSXYosemite,ElCapitan

serialport:cu.wchusbserial1410–  CH34x_Install_Windows_v3_4.zip:Windows7

serialport:COM3–  CH340_LINUX.zip:Ubuntu14.04

serialport:/dev/ttyUSB0

•  Otherdriversareavailablefromhttp://sparks.gogo.co.nz/ch340.html

6.101 Spring 2018 Lecture 5 34

// driver install make sudo make load

ArduinoLab

6.101 Spring 2018 Lecture 5 35

common normally closed

Connect switch to Arduino and control LED