EDC Chapterwise Formulas

7/16/2019 EDC Chapterwise Formulas

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ELECTRONIC DEVICES AND CIRCUITS

BRIEF NOTES

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MATERIALS UNIT – I :: ELECTRON DYNAMICS: CRO

¾ kg−

, ‘F’ force on electron in uniform electric field ‘E’ 19 311.602 10 , 9.1 10e C m

−= × = ×

¾ F=eE; accelerationeE

am

=

¾ If electron with velocity ' 'v moves in field ' ' E making an angle ' 'θ can be

resolved to , cossinv vθ θ .

¾ Effect of Magnetic Field ‘B’ on Electron.

¾ When B & Q are perpendicular path is circular2

; 'mv m

eriod t 'r Pπ

Be Be= =

¾ When slant with ' 'θ path is # Helical. ¾ EQUATIONS OF CRT

¾ ELECTROSTATIC DEFLECTION SENSITIVITY2

lL

dV = e

a

S

¾ MAGNETIC DEFLECTION SENSITIVITY2

e

m

a

S lLmV

=

2eV v

m= ¾ Velocity due to voltage V,

¾ When E and B are perpendicular and initial velocity of electron is zero, the path is

Cycloidal in plane perpendicular to B & E. Diameter of Cycloid=2Q, whereu

Qω

= ,

E u

B= ,

Be

mω = .

UNIT – II :: SEMICONDUCTOR JUNCTION

¾ ,i eS G have 4 electrons in covalent bands. Valency of 4. Doping with trivalent

elements makes ' ' p , Pentavalent elements makes ' 'n semiconductor.

¾ Conductivity p p( )ne nσ μ = μ + where ,n p are concentrations of Dopants.

&n pμ μ are mobility’s of electron and hole respectively.

Diode equation

1d

T

V nV

d s I I e⎛ ⎞

= −⎜ ⎟⎝ ⎠

;T V q

=kT

K= Boltzman Constant

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¾ 2

; lnd T Ad o

d i

V V N kT r V

I I q

P N ⎛ ⎞Δ= = = ⎜ ⎟

Δ ⎝ ⎠n

¾ 9C

−× 0 10 273; 1.602 10T C q= + =

¾ Diode drop changes0@ 2 2 /mv C , Leakage current. s I doubles on

010 C

¾ Diffusion capacitance isd

dqc

dv= of forward biased diode it is I ∝

¾ Transition capacitanceT

C is capacitance of reverse biased dioden

V −∝ 1 1

2 3to n =

¾ RECTIFIERS

¾ COMPARISION

HW FW CT FW BR

DC V mV

π

2 mV π

2 mV

π

rmsV 2

mV

2

mV

2mV

γ Ripple factor

1.21 0.482 0.482




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η

Rectification efficiency40.6% 81% 81%

PIV Peak Inverse Voltage m m mV 2V V

UNIT – III :: FILTERS

¾ Harmonic Components in FW Output, 0

2 4 1 1cos 2 cos 4

3 15mV

t wπ π

.....v w t ⎧ ⎫

+= − +⎨ ⎬ ⎩ ⎭

Capacitance Input Filter,1

4 3 L

f CRγ =

¾ ZENER DIODE

Inductor Input Filter,3 2

L R

Lγ

ω =

C L

ve+ ve−

Critical inductance is that value at which

diode conducts continuously, in or

half cycle.

LC FILTER,

22

12 LC γ

ω = or 1.2 , 50 , , . for Hz L in H C in F

LC μ

π FILTER, 1 22

. .3

C C

L L

X X

R X γ =

RC FILTER, 1 22. .C C

L

X X

R Rγ =

FWD Bias Normalis

Diode 0.7 V Drop

Reverse Bias

z z Zener drop V forV V = >

1 2

1 2

2. . .....

3n

n

cc c

L L L

X X X

X X X γ = LC LADDER,




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¾ ZENER REGULATOR

¾ ;i zs i z

s

V V I V V

R

−= >>

¾ z z

z

V r

I Δ

=Δ

¾ TUNNEL DIODE

¾ Conducts in , f r b b

, Quantum mechanical tunneling in region a-0-b-c.

¾ -ve resistance b-c, normal diode c-d.

p I = peak current, v I = valley current; =peak voltage≈

65 mV, =valley voltage0.35 V. Heavy Doping, Narrow Junction , Used for switching & HF oscillators.

pv vv

¾ VARACTOR DIODE

Used in reverse bias & as tuning variable capacitance.

¾ ( )

T

T R

C V V

=+

n

K ; n=0.3 for diffusion, n=0.5 for alloy junction,

1

oT n

R

T

C C

V V

=⎛ ⎞+⎜ ⎟⎝ ⎠

¾ 25

BC

C is figure of merit, Self resonance

1

2o

S T

f L C π

=

¾ PHOTO DIODES




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¾ Diode used in reverse bias for light detection.

¾ Different materials have individual peak response to a range of wave lengths.

UNIT - IV

¾ BJT, Bipolar Junction Transistor has 2 Junctions: BE, BC

¾ Components of current are ,nE pE I I at EB junction where nE nE

nE pE E

I I

I I I γ = =

+

¾ γ = Emitter efficiency,* nc

nE

I

I β = transportation factor.

¾ / B / ; E f b B= =C r b

¾ Leakage currents : , ,CBO CEO EBO I I I

¾ ( )1CEO CBO I I β = +

e b c I I I = +

;c c

e b

I I

I I α β = =

Doping Emitter Highest

Base Lowest

e c b I I I > >




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¾ 3 Configurations are used on BJT, CE, CB & CC

¾ ¾ Common Emitter, VI characteristics

¾ 0; ce BE i ie e ce

B c

V V R h r r r

I I β

ΔΔ= = = = =

Δ Δ

AC Equivalent Circuit

¾ COMMON BASE VI CHARACTERISTICS

¾ ;1

C

E

I

I

β α α

β = =

+

CE

C V

B

I

I β =

Input Characteristics Circuit Output Characteristics

AC Equivalent Circuit




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¾ ; ;V CB

C cb EBib e fb cb

E e c

I V V h r h r

Δ

I I I

Δ= = =

Δ Δ=

UNIT - V

¾ h- parameters originate from equations of amplifier

2 2 0 2,i i i r f i

v h i h v i h i h v= + = +

&iv ii

2

, ,ib

are input voltage and current

2&v i are output voltage and current

¾ ih → input impedance

ie ich h h ( )1 er +, ,e er r β β ⎡ ⎤⎣ ⎦

¾ f h → current gain , , fe fb fc

h h h ( )1, , β α β +⎡ ⎤⎣ ⎦

¾ r h → reverse voltage transfer , ,re rb rc h h h

¾ oh → output admittance , ,ob och h

oe h

¾ FIELD EFFECT TRANSISTOR, FET is Unipolar Device

Construction n-Channel p-Channel

¾ S=Source, G=Gate, D=Drain

¾ GS Junction in Reverse Bias Always ¾

gsV Controls Gate Width

COMPARISON

BE BC

SATURATION f/b f/b

ACTIVE f/b r/b

CUT OFF r/b r/b

AMPLIFIER COMPARISON

CB CE CF

i R LOW MED HIGH

I I A A 1 β β +

V A High High <1

o R High High low




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¾ VI CHARACTERSTICS

Tr ansfer Characteristics Circuit Forward Characteristics

¾ Shockley Equation

¾ 2

1 gs

d dss

p

V I I

V ⎛ ⎞= −⎜ ⎟⎜ ⎟⎝ ⎠

, 0 1 gs

m m

p

V g g

V ⎛ ⎞= −⎜ ⎟⎜ ⎟⎝ ⎠

¾ MOSFET: Metal Oxide Semiconductor FET, IGFET

De pletion Type Mosfet Symbols Enhancement Mosfet

¾ Depletion Type MOSFET can work width 0gsV > and 0gsV <

MOSFET JPET

High1010i R = 810−

Transfer Forward

Characteristics Characteristics

¾ Enhancement MOSFET operates with,gs t V V > ,

t V Threshold Voltage=

0 50 R k = Ω 1m≥ Ω

DepletionEnhancement Mode

DepletionMode

Delicate Rugged




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Forward Characteristics Transfer Characteristics

( ) , DS GS V sat V V = − T ( )2

( )ds GS T

I ON K V V = −

D JFET I Table

UNIT – VI :: BIASING in BJT & JFET

¾ Fixing Operating Point Q is biasing

Fixed Bias Emitter Stabilized Feedback Bias

CC B B BE V I R V = + Fixed Bias ( )1CC C B B B BE V R I I R β = + + +V

( )1 ReCC B B BE

V I R V β = + + +

gsV D I

0 DSS I

0.3PV

2 DSS I

0.5PV

4 DSS I

PV 0

COMPARISIONS

BJT FET

Current controlled Voltage controlled

High gain Med gain

Bipolar Unipolar

Temp sensitive Little effect of T

High GBWP Low GBWP




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; E E B BE C

E V V V V I R= − ≈

2

1 2

CC B

V RV

R R=

+,

( )( )1 Re

.

Vcc Rc Ib

Ib Rb Vbe

β = + +

+ +

VOLTAGE DIVIDER BIAS EMITTER STABILIZEDFIXED BIAS

STABILITY EQUATIONS

¾ 1 0 2 3c c BE I S I S V S β

Δ = Δ + Δ + Δ

( )¾ 1 2 3; ;C C C

CO BE

I I I S S S

I V β

Δ Δ= =

Δ Δ

Δ=

Δ, STABILITY FACTOR

1

1 B

C

dI

dI

β

β

+=

−S

¾ S must be as small as possible, Most ideal value =1

¾ How to do determine stability factor for bias arrangement? Derive B

C

dI

dI and

substitute in S

¾ Amplifier formulae: l I V

i

Z A A

Z

= ,i Z measured with output shorted

¾ 0Z measured with input shorted

¾ feh or CE amplifier IA β ≅ ;

¾ ;i Z re β = T e

V r ;

I = ; L

R

ve

Ar

= −

CB amplifier 1A ; Lv i

e

R A Z

r α = =

CC a ( )

; er = ¾

IA 1 ; 1V i

A ;ieh R

β = + = − ( )1i fe E ie

R h R h= + + ¾ mplifier

¾ H Parameter Model CE

¾ ; fe

h z+

1 I

oe l

h A = L

V fe

ie

Z A h

h=

¾ CB amplifier ; ; . Li ib I fb V fb

ib

R R h A h A h

h= = =

¾ FET

¾ CS amplifier 0 d ( )|| ;V m d d A g R r = − Z R=

¾ Common Gate Amplifier ,

1

s R

g R

V m d i

m s

A g R Z = =

+




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¾ Common Drain1

;1

m sV o

m s m

g R A Z

g R g= =

+

¾ RC Coupled Amplifiers

¾ If cut off frequency 1

1

2 f RC π = ,

1 1

1

1

tan ; 1

f

A f f j

f φ

− ⎛ ⎞

= =⎜ ⎟⎝ ⎠ ⎛ ⎞+ ⎜ ⎟⎝ ⎠

¾ ,6 / ,20 /Slope dB octave dB decade= f Octave= 22

or f

¾ f β is beta cut off frequency where 0.707

feh falls by→

¾ f α is α cut off frequency where 0.707α =

¾ t

f is 1 fe

h = gain bandwidth product.

UNIT – VII :: FEED BACK AMPLIFIERS

¾ Amplifier gain stands for any of Voltage amplifier, Current amplifier, Trans resistanceTrans admittance amplifier

0

0

; ;1

X

¾ +

−

Ve feed back amplifier depends on |1 1 e f | 1 ,b b A ve f v β + > − <

)

+

¾ Feed back reduces noise distortion, gain variation due to parameters, increases BW.

(1 A β + is called de-sensitivity factor.

¾ Feed back amplifiers

Voltage series, voltage shunt; Current series, current shunt

UNIT – VIII :: OSCILLATORS

¾ Barkausen Criterion for oscillation loop gain =1, θ =00, 3600.

f

f

i

X A A A

A X X β

β = = =

+

f

i s X X X = −

for voltage, current series

( )1 f i i z z A β = +

1 f

A A

A β =

+, for all

1 f

i

i

z z

A β =

+, for voltage or current shunt

( )1 f o o z z A β = + , for current series, shunt

0

1 f o

z z

A β =

+

, for voltage series and shunt.




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¾ HARTLEY OSCILLATOR

2

1

L

L β =

1

2 T

f L C π

= 1 2T L L L M = + ± , ;, ,

COLLPITS OSILLATOR,

1 2, L L replaced by C ,1 2,C

1

2 T

f LC π

=C replaced by L;

¾ CRYSTAL OSCILLATORS

¾ Tuned ckt replaced with Crystal

1s

LC ω = ,

1 p

T LC ω =

¾ Phase shift oscillator

FET MODEL

12 6

f RC π

= 29 A =, ,

Minimum RC sections 3

BJT MODEL1

42 6 C

f R

RC R

π

=⎛ ⎞

+ ⎜ ⎟⎝ ⎠

, 29 A = ,

Minimum RC sections 3

¾ Wein Bridge Oscillator

1 2 1 2

1

2 f

R R C C π = ,

if R1=R2=R, C1=C2=C ,1

2 f

RC π = ;

13 A

β = =

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EDC Chapterwise Formulas