EDC Chapter Wise Formulas

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Page No. 1

ELECTRONIC DEVICES AND CIRCUITS BRIEF NOTES

SEE WWW.UANDISTAR.BLOGSPOT.COM FOR MORE JNTU MATERIALS UNIT – I :: ELECTRON DYNAMICS: CRO ¾ ¾ ¾

e = 1.602 ×10−19 C , m = 9.1×10−31 kg , ‘F’ force on electron in uniform electric field ‘E’ eE F=eE; acceleration a = m If electron with velocity ' v ' moves in field ' E ' making an angle 'θ ' can be resolved to v sin θ , v cos θ .

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Effect of Magnetic Field ‘B’ on Electron.

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When B & Q are perpendicular path is circular r =

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

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ELECTROSTATIC DEFLECTION SENSITIVITY Se =

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MAGNETIC DEFLECTION SENSITIVITY S m = lL

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Velocity due to voltage V, v =

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

mv 2π m ; Period ' t ' = Be Be

lL 2dVa

e 2mVa

2eV m

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

u=

Q=

u

ω

,

E Be , ω= . m B UNIT – II :: SEMICONDUCTOR JUNCTION

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Si , Ge have 4 electrons in covalent bands. Valency of 4. Doping with trivalent Pentavalent elements makes ' n ' semiconductor. elements makes ' p ' ,

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Conductivity

σ = e ( n μn + p μ p )

μn & μ p

mobility’s of electron and hole respectively.

are

where

n, p are concentrations of Dopants.

Diode equation

⎛ Vd ⎞ I d = I s ⎜ e nVT − 1⎟ ⎝ ⎠

-1-

VT =

kT ; K= Boltzman Constant q

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ΔVd VT kT ⎛ N A N P ⎞ = ; Vo = ln ⎜ ⎟ ΔI d I q ⎝ ni 2 ⎠

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rd =

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T = 00 C + 273; q = 1.602 × 10−19 C

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Diode drop changes @ 2.2mv / C ,

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Diffusion capacitance is cd =

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Transition capacitance CT is capacitance of reverse biased diode ∝ V

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RECTIFIERS

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COMPARISION

0

0

Leakage current I s doubles on 10 C

dq of forward biased diode it is ∝ I dv

HW

VDC

Vm

Vrms

Vm

γ Ripple factor

π

FW CT

FW BR

2Vm

2Vm

π

Vm

π

Vm

2

2

2

1.21

0.482

0.482

-2-

−n

n = 1 to 1 2 3

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Page No. 3

η Rectification efficiency

40.6%

81%

81%

Vm

2 Vm

Vm

PIV Peak Inverse Voltage

UNIT – III :: FILTERS

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Harmonic Components in FW Output,

v0 =

2Vm

π

−

4 ⎧1 1 ⎫ ⎨ cos 2wt + cos 4 wt + .....⎬ 15 π ⎩3 ⎭

Capacitance Input Filter,

Inductor Input Filter,

γ=

γ=

1 4 3 f CRL

RL 3 2 ωL

Critical inductance

LC is that value at which diode conducts continuously, in + ve or −ve half cycle. LC FILTER,

γ=

2 1.2 , for 50 Hz , L in H , C in μ F . or LC 12ω LC 2

γ=

LC LADDER,

π

FILTER,

γ=

RC FILTER,

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ZENER DIODE

FWD Bias Normal si Diode 0.7 V Drop Reverse Bias

Zener drop = Vz forV > Vz -3-

Xc 2 X c1 X c2 . . ..... n X Ln 3 X L1 X L2

2 X C1 X C2 . . 3 RL X L

γ = 2.

X C1 X C2 . RL R

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ZENER REGULATOR

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Is =

¾

rz =

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TUNNEL DIODE

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Conducts in

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

Page No. 4

Vi − Vz ;Vi >> Vz Rs ΔVz

ΔI z

f b

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

I p = peak current, I v = valley current; v p =peak voltage ≈ 65 mV, vv =valley voltage 0.35 V. Heavy Doping, Narrow Junction , Used for switching & HF oscillators.

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VARACTOR DIODE

Used in reverse bias & as tuning variable capacitance.

K

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CT =

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CB 1 is figure of merit, Self resonance f o = C25 2π LS CT

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PHOTO DIODES

(VT + VR )

n

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

-4-

Co ⎛1 + VR ⎞ ⎜ VT ⎟⎠ ⎝

n

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Page No. 5

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Diode used in reverse bias for light detection.

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

UNIT - IV ¾

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

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Components of current are I nE , I pE at

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γ = Emitter efficiency, β * =

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BE = f / b; BC = r / b

EB junction where γ =

I nc transportation factor. I nE

Ie = Ib + Ic

α=

Ic I ;β = c Ie Ib

Doping Emitter Highest Base Lowest

Ie > I c > Ib ¾ ¾

Leakage currents : I CBO , I CEO , I EBO

I CEO = (1 + β ) I CBO

-5-

I nE I = nE I nE + I pE I E

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Page No. 6

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

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Common Emitter,

VI characteristics

β =

¾

Ri = hie =

IC IB

VCE

ΔV ΔVBE = β re ; rce = r0 = ce ΔI B ΔI c

Input Characteristics

Circuit

Output Characteristics

AC Equivalent Circuit

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COMMON BASE VI CHARACTERISTICS

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α=

IC β ;α = IE 1+ β -6AC Equivalent Circuit

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hib =

I ΔVEB = re ; h fb = C Ie ΔI E

VCB

Page No. 7

; rcb =

ΔVcb ΔI c

AMPLIFIER COMPARISON COMPARISON BE SATURATION ACTIVE CUT OFF

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CB

CE

CF

Ri

LOW

MED

HIGH

AI

AI

β

β +1

AV

High

High

0 and Vgs < 0 MOSFET

JPET

High Ri = 10

10

Transfer Characteristics

¾

−108

R0 = 50 k Ω

≥ 1mΩ

Depletion Enhancement Mode

Depletion Mode

Delicate

Rugged

Forward Characteristics

Enhancement MOSFET operates with, Vgs > Vt , Vt = Threshold Voltage

-8-

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Page No. 9

Forward Characteristics

Transfer Characteristics

VDS ( sat ) = VGS − VT , I ds (ON ) = K (VGS − VT )

2

COMPARISIONS

JFET I D Table Vgs

ID

0

I DSS

0.3 VP

I DSS

0.5 VP

I DSS

VP

BJT

FET

Current controlled

Voltage controlled

High gain

Med gain

Bipolar

Unipolar

Temp sensitive

Little effect of T

High GBWP

Low GBWP

2 4

0

UNIT – VI :: BIASING in BJT & JFET ¾

Fixing Operating Point Q is biasing

Fixed Bias

VCC = I B RB + VBE

Emitter Stabilized Fixed Bias

VCC = I B RB + VBE + ( β + 1) Re

-9-

Feedback Bias

VCC = ( β + 1) RC I B + I B RB +VBE

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Page No. 10

VB =

VCC R2 , R1 + R2

VE = VB − VBE ; I C ≈

VE

RE Vcc = ( β + 1)( Rc + Re ) Ib + Ib.Rb + Vbe

VOLTAGE DIVIDER BIAS

EMITTER STABILIZED FIXED BIAS

STABILITY EQUATIONS ¾

ΔI c = S1ΔI c 0 + S2 ΔVBE + S3 Δβ

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S1 =

¾

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

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How to do determine stability factor for bias arrangement?

( β + 1) ΔI C ΔI C ΔI ; S2 = ; S3 = C , STABILITY FACTOR S = dI ΔI CO ΔVBE Δβ 1− β B dI C Derive

substitute in S

AV = AI

Zl , Z i measured with output shorted Zi

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Amplifier formulae:

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Z0 measured with input shorted

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CE amplifier A I ≅ h fe or β ;

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VT R ; Av = − L ; re I R CB amplifier A1 = α ; Av = L ; Z i = re re Z i = β re; re =

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CC amplifier A I = ( β + 1) ; AV = 1 −

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H Parameter Model CE

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AI =

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CB amplifier Ri = hib ; AI = h fb ; AV = h fb .

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FET

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CS amplifier AV = − g m ( Rd || rd ) ; Z 0 = Rd

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h fe 1 + hoe zl

; AV = h fe

Common Gate Amplifier

hie

Ri

; Ri = ( h fe + 1) RE + hie

ZL hie

AV = g m Rd , Z i =

RL hib

Rs 1 + g m Rs

- 10 -

dI B and dI C

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AV =

Page No. 11

g m Rs 1 ; Zo = 1 + g m Rs gm

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Common Drain

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RC Coupled Amplifiers

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If cut off frequency

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Slope = 6dB / octave, 20dB / decade ,

f1 =

1 , 2π RC

φ = tan −1 ⎛⎜ f1 f ⎞⎟ ; A = ⎝ ⎠ 1+

1 f j ⎛⎜ 1 ⎝

⎞ f ⎟⎠

Octave= f

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or 2 f 2 f β is beta cut off frequency where h fe → falls by 0.707

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fα is α cut off frequency where α = 0.707

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ft is h fe = 1 gain bandwidth product. UNIT – VII :: FEED BACK AMPLIFIERS

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

Af =

X X A ; A= 0 ; β = f Xi X0 1 + Aβ

Xi = Xs − X f ¾

+

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

−

Ve feed back amplifier depends on |1 + Aβ | > 1 − ve f b , < 1 + ve f b

(1 + Aβ ) ¾

is called de-sensitivity factor.

Feed back amplifiers Voltage series, voltage shunt; Current series, current shunt

for voltage, current series zi f = zi (1 + Aβ ) A , for all 1 + Aβ zi , for voltage or current shunt zi f = 1 + Aβ zo f = zo (1 + Aβ ) , for current series, shunt Af =

zo f =

z0 , for voltage series and shunt. 1 + Aβ

UNIT – VIII :: OSCILLATORS ¾

Barkausen Criterion for oscillation loop gain =1, - 11 -

θ =00, 3600.

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Page No. 12

HARTLEY OSCILLATOR

f =

1 , 2π LT C

LT = L1 + L2 ± M , ; β =

L2 , L1

COLLPITS OSILLATOR,

L1 , L2 replaced by C1 ,C2 , C replaced by L; f =

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CRYSTAL OSCILLATORS

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Tuned ckt replaced with Crystal

1 2π LCT

1 , LC 1 ωp = LCT

ωs =

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Phase shift oscillator

FET MODEL f =

1 , A = 29 , 2π 6 RC

Minimum RC sections 3

f =

BJT MODEL 1 ⎛ 4R ⎞ 2π RC 6 + ⎜ C ⎟ ⎝ R ⎠

, A = 29 ,

Minimum RC sections 3

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Wein Bridge Oscillator

f =

1 , 2π R1 R2C1C2

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

- 12 -

1 1 ; A= =3 β 2π RC