Lec 0 Recap Summer School

7/27/2019 Lec 0 Recap Summer School

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RecapElectric circuits

Network Analysis

Electronics -I


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Introduction Sources

Voltage/Current Sources Independent/Dependent

Electric Signals Analog/Digital Signals

DC/AC/Time Varying/Periodic Signals

Element Laws/Connection Laws Ohms Law & Kirchhoffs Laws

Voltage Divider & Current Divider Circuits

Techniques of Circuit Analysis Nodes/Branches/Loops/Meshes

Source Transformations /Superposition


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Electric Signal

(Voltage & Current)

Role Conversion

Transmission

Utilization

Use Represent

Amplified Manipulate/Process

Transmit

Store

Energy

Information (Signal)


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Circuits Configuration

Circuit Element

Interconnection

Connecting Wires

Zero Resistance Same Potential

Current entering = Current Leaving


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Branches

Each circuit element constitutes a Branch Branch Current (Direction) / Voltage (Polarity)

Nodes

Two or more elements having a common connection.

Simple Node (ONLY Two leads converge to a node)

Nodes are connected with un-interrupted wire Node Potential / Current

Label the Nodes

Reference / Common Node Largest number of

connections (Zero Potential or earth-ground)



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Branch Voltage

Node Voltage


BAAB vvv

CR vv ,

ABBA vvv vB Node B voltage wrt common (ground) Node


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Voltage / Current Sources

A Voltage source maintains a prescribed voltage

regardless of the load current.

Unequal Voltage Sources can be connected in

series but must never be connected in parallel.

A current source maintains a prescribed current

regardless of the load voltage. Unequal current Sources can be connected in

parallel but must never be connected in series.


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Independent Sources

DC Voltage

AC Voltage

Battery

DC Current

AC Current


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Dependent Sources

VCVS

CCVS

kvvx

kvix kivx

kiix

CCCS

VCCS


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Circuit Laws

Element Laws Relates the terminal voltage and current

of individual element --- Ohms Law,Capacitance Law, Inductance Law

Kirchhoffs Laws Relates the voltages and currentsshared at the interconnectionsKirchhoffs Current and Voltage Laws

dt

tdvCti

)()( dt

tdiLtv )()( R

vi


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Kirchhoffs Current Laws

(KCL) The algebraic sum of the current entering

any node is zero

At any instant, the sum of all currentsentering a node must equal the sum of allcurrents leaving that node

n

outn

in ii


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Power Conservation

The sum of all absorbedpowers, atany instant, equal the sum of all

releasedpowers

releasedabsorbed pp

Ci it A l i


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Circuit Analysis

Series or parallel impedance reduction

Voltage or current divider formula

Node or Loop methods

Thevenin or Norton reductions


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Notation Summarized

Notat ion

Base (col lector)

Voltage wit h

respect to

Emitter

Base (col lecto r)

Current toward

electrod e from

external circ ui t

Instantaneous Total Value (DC

+ AC) vB (vC) iB (iC)Quiescent Value (DC) VB (VC) IB (IC)Instantaneous Value ofvarying component (AC) vb (vc) ib (ic)Effective Value of varying

components Vb (Vc) Ib (Ic)Supply Voltage (Magnitude)

VBB (VCC)


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Introduction

Natural Response of Circuits Transient Response

Steady State Response

Domains Time Domain

Physical Frequency Domain (j

) Complex Frequency Domain (s)

Laplace Transform


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Introduction

Practical Voltage/Current Sources Maintains its rating Internal resistance Loading Effects

Equivalent Resistance Series /Parallel Reduction or by inspection Test Source with dependent source

Apply a test source by suppressing independentsources

Suppressing Sources


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DIODE


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BJT Three terminal device

Basic Principle

Voltage between two terminals controls current flowing in

the third terminal.

Device is used in discrete and integrated circuits and

can act as :

Amplifier

Logic Gates

Memory Circuits

Switches

Invented in 1948 at Bell Telephone Industries


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Device Structure & Physical Operation

npn & pnp Transistor

Three terminal ---- Emitter, Base, Collector

Consists of two pn junctions

np-pn -------- npn pn-np -------- pnp

Junctions Emitter Base Junction (EBJ)

Collector-Base Junction (CBJ)

Modes Cut-off

Active

Saturation


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A simplified structure of the npn transistor.


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TWO EXAMPLES OF DIFFERENT SHAPES OF TRANSISTOR


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An npn trans is tor

A & t i t


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A pnp & npn trans is tor


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npn/pnp Transistor


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npn Transistor

T

BE

vv

SC eIi

BCE iii

1

1

BCii


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Modes of operation

Amplification of Signal

Operation inActive Mode

Vvv

Vvv

CEsatCE

BEonBE

3.0

7.0


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Single Stage BJT Amplifier

Three Configurations

Common Emitter (CE)

Common Emitter (CE) with EmitterResistance

Common Base (CB)

Common Collector (CC)


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Amplifier ClassificationThree families of amplifiers:

1. Common-emitter/common-source (C-E/C-S) circuits Invert ingamplifiers

These amplifiers provide moderate/high voltage gain, inputresistance, and output resistance.

2. Common-base/common-gate (C-B/C-G) circuits Noninvert ingamplifiers

These amplifiers provide moderate/high voltage gain, low inputresistance, and high output resistance.

3. Common-collector/common-drain (C-C/C-D) circuits Fol lowercircuits (emitter-follower/source-follower).

These amplifiers are the single-transistor equivalents of the op ampvoltage follower because they provide voltage gain ofapproximately 1, high input and low output resistance.


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Small Signal Model : BJT

Model

TModel


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Single Stage BJT AmplifierSmall Signal Output

Model Resistance

Pi Model Include

T Model Include

T Model Dnt Include

T Model Dnt Include

Common Emitter (CE)

Common Collector (CC)

Common Emitter (CE)

with Emitter Resistance

Common Base (CB)


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Application (Steps) : Small Signal Model

Suppress ac independent sources ac Voltage Sources be short circuited

ac Current Sources be open circuited

External and internal Capacitors be Open circuited

Determine DC operating Point IC

Suppress DC independent sources

DC Voltage Sources be short circuited DC Current Sources be open circuited

External Capacitors be short circuited

Internal Capacitors be open circuited

Replace BJT with small signal Model

Analyze the resulting circuit of find voltage gain & input/output resistance

E

T

m

e

B

T

m

ebbemc

T

Cm

I

V

gr

I

V

gr

iivgi

V

IgCalculate

CE

C

B

SC

III

II

II

B

T

BE

V

V

eActive Mode Verification

VBE > 0.7 V

VC> VB-0.4 V

Small Signal Analysis


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MOSFET Small Size

Manufacturing process is simple

Requires comparatively low power

Implement digital & analog functions with a fewerresistors very large scale Integrated (VLSI) circuit

Study Includes

Physical structure Operation

Terminal characteristics

Circuit Models

Basic Circuit application


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The enhancement-type NMOS transistor:


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n-channel MOSFET

iD = iS, iG = 0


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Modes of Operation

Amplification of Signal

Operation inActive Mode

DC Analysis


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DCAnalysis

Suppress the AC (independent Sources)

Short Circuit Voltage Sources

Open Circuit Current Sources

Calculate DC Node VoltagesVC,VB, VE

& Loop Currents IC,IB,IE

Open Circuit the External & Internal Capacitors

Redraw the circuit

Purpose :

To find out mode of operationTo determine the operating point

To Calculate gm, rpi, re


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Small Signal Model

Suppress the DC (independent Sources)

Short Circuit Voltage SourcesOpen Circuit Current Sources

Short Circuit the External Capacitors

Redraw the Circuit by replacing

Transistor with its Small Signal Model

Carry out Circuit Analysis to

Find Rin, Rout, & Transfer Function

Purpose :

To determine Rin, Rout, &Transfer Function(Voltage Gain)

Open Circuit the Internal Capacitors


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The Four Amplifier Types

Small Signal T Model : NMOSFET


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Small Signal T Model : NMOSFET


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Small Signal Models

T Model

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