ece/eee/instr f244 micro electronics circuits

BITS Pilani Dubai Campus

ECE/EEE/INSTR F244 Micro Electronics Circuits

Dr Jagadish Nayak

BITS Pilani Dubai Campus

Introduction

MicroElectronics Circuits Lecture 1 by Dr Jagadish Nayak BITS Pilani, Dubai Campus

۞ Transistor Circuits for micro electronics level

۞ Study BJT and MOSFET amplifier characteristics

۞ Multistage amplifiers

۞ Feedback amplifies

۞ Output stage amplifies

۞ Power amplifiers

۞ Op-Amps

۞ Frequency responses characteristics of all the above

Course outline


Construction and working principles of BJT, MOSFET

Elementary circuit theory

Concept of frequency

Active and passive elements

Concepts of Voltage, current, and Power

Pre-requisites


Entire Semester lecture and Tutorial plan is available

There will be three lecture hours and one tutorial hour in a

week.

Attendance will be taken for both lecture and Tutorial hour

Every topics can be practically implemented by a software

tool called as PSPICE.

Students are supposed to learn this tool by themselves

Introduction class on PSPICE is taken in the Tutorial class

only

All students must submit the assignment on PSPICE

PSPICE software is available freely as Limited student

version from the website

Lecture Hour and Tutorial


What is an amplifier ?? – System which amplify a small quantity into large quantity

In Electronics we are more interested on amplification of

Electrical quantities such as voltage, current and Power.

BJT and MOSFETs can be used as an amplifier.

These components are the basic building blocks of the

amplifier.

Amplifier circuits are embedded in small package in

many stages and available in micro level.

Design of this amplifier circuit in micro level is in High

demand in present scenario.

Introduction to Amplifiers


Signal Amplification

Let us consider a Microphone (Transducer),

Output of the microphone is raised to mV, which is called as

signal amplification.

The amplifier has to be linear.

General Characteristics


Let output of the amplifier be v0(t) for an input of vi(t) at time

instant t

The input output relation is

v0(t)=A vi(t)

Where A is called as Gain of the amplifier.

General Characteristics


Circuit Symbol


Consider following amplifier

Voltage gain

Voltage Gain

I

vv

vA 0


Transfer characteristics


Power Gain, Voltage gain

I

i

II

I

L

p

i

iAGainCurrent

iv

iv

PPowerInput

PPowerLoadAGainPower

0

00

)(

)(

)()(


Voltage gain in decibels =20 log |Av|

Current gain in decibels =20 log |Ai|

Power gain in decibels =10 log |Ap|

Gains in Decibels


Amplifier need power supplies to operate. Typical amplifier

requires two power supplies as shown below

Power Supplies for the amplifiers


The net dc power delivered to the Load is

Pdc=V1I1+V2I2

If the power dissipated in the amplifier is denoted by Pdiss

The power balance equation for the amplifier is

Pdc+PI=PL+Pdiss

– Where PI=Power drawn from the signal source (normally

small)

– And PL is Power delivered to the Load

Amplifier efficiency


100xdc

L

P

P


Amplifier Saturation

An amplifier transfer characteristic that is linear except for output saturation


Practical amplifier may exhibit non-linearity in its transfer

characteristics.

Non-Linear transfer characteristics and Biasing


The operating point is selected by the biasing of the transistor

amplifier circuits. This is done as shown below.


inputousinstantanitotal)(Where

)()(

tv

tvVtv

I

iII

inputousinstantanitotal)(Where

)()(

tv

tvVtv

O

oOO

QatI

O

v

ivo

dv

dvA

tvAtv )()(


Av is slope of the almost linear segment of the transfer

curve.

So for the linear amplification, there is a limitation, what is

that

The input signal must be kept sufficiently small so that

input amplitude will not reach non-linear portion.

This distortion is undesirable

This approximation is called as small-signal approximation.


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