Ramakant A.
Gayakwad, “Op-amps
and Linear Integrated Circuits”, PHI
Publication.
1. The basic operational amplifier
2. Advantages of opamp over transistor
3. Characteristics of Ideal Operational Amplifiers
4. Block diagram of opamp
5. Symbol and pin-diagram of opamp
6. Single ended input and double ended input operation
7. Internal circuit of 741 Op-amp.
8. Types of Ics
9. Manufacturers’ designations and package types for Ics
10. Power supplies for ICs.
The opamp is a direct-coupled high gain amplifier.
The opamp is a versatile device that can be used to
amplify dc as well as ac input signals and was originally
designed for performing mathematical operations such
as addition, subtraction, multiplication and integration.
Thus the name operational amplifier stems form the
use for these mathematical operation and abbreviated
to op-amp.
With the addition of suitable external feedback
components, the opamp can be used for a variety of
applications such as amplification, active filters,
oscillators, comparators, regulators and others.
Less power consumption
Costs less
More compact
More reliable
Higher gain can be obtained
Easy design
An ideal op-amp would exhibit the following electrical
characteristics:
Infinite Open loop Voltage Gain A0 .
Infinite input resistance Ri so that almost any signal source can
be drive it and there is no loading of the preceding stage.
Zero output resistance R0 so that the output can be drive an
infinity number of other devices.
Zero output voltage when input is zero.
Infinity bandwidth so that any frequency signal from 0 to ∞ Hz
can be amplified without attenuation.
Infinity common-mode rejection ratio so that the output
common-mode noise voltage is zero.
Infinity slew rate so that output voltage changes occur
simultaneously with input voltage changes.
Zero drift of characteristics with temperature.
Input Stage:
Increases the CMRR.
Most of the gain is adjusted.
Provides the input impedance very high.
Intermediate Stage:
Driven by output of First stage.
Further increases the gain.
Level Shifting:
Suppress the dc level downward to zero volt with
respect to ground
Consisting of current amplifiers as emitter followers.
Output Stage:
This stage increases the output voltage swing and the
current in supplying capability of the amplifiers.
Provides low output impedance.
Single-ended input operation results
when the input signal is connected to
one input with the other input connected
to ground.
It is possible to apply signals at each
input this being a double-ended
operation.
Integrated circuit meaning that all the
components in the circuit are fabricated
on the same chip.
Ics are very popular and widely used in
all types of electronic equipments now a
days.
Classification On the basis of applications
ICs are of two types namely: Linear Integrated Circuits and
Digital Integrated Circuits.
Linear IC:
Linear IC’s are used in cases when the relationship between
the input and output of a circuit is linear. An important
application of linear IC is the operational amplifier commonly
referred to as op-amp.
Digital IC:
When the circuit is either in on-state or off-state and not in
between the two, the circuit is called a digital circuit. IC’s used
in such circuits are called digital IC’s. They find wide
applications in computers and logic circuits.
classification of integrated circuits based on the fabrication
techniques used.
1. Monolithic Integrated Circuits
The word ‘monolithic’ comes from the Greek words
‘monos’ and ‘lithos’ which means ‘single’ and ’stone’. As
the name suggests, monolithic IC’s refer to a single stone
or a single crystal. The single crystal refers to a single chip
of silicon as the semiconductor material, on top of which
all the active and passive components needed are
interconnected.
2. Hybrid or Multi-chip Integrated Circuits
As the name suggests, the circuit is fabricated by
interconnecting a number of individual chips. Hybrids ICs
are mostly used for high power audio amplifier
applications from 5 Watts to more than 50 Watts.
ICs can be classified on the basis of Technology
used:
ICs can be classified on the basis of their device count
(chip size) as given below:
Small scale integration (SSI)— < 10 gates/chip.
Medium scale integration (MSI)— < 100 gates/chip.
Large scale integration (LSI)— > 100 gates/chip.
Very large scale integration (VLSI)— > 1,000 gates/chip.
IC package types
Pin Identification:
In ordering a IC following information must
be specified
Device type
Package type
Temperature range
Most linear Ics (particularly op-amps) require
both a positive and negative power supply for
proper operation of the circuit.
Digital Ics on the other hand, generally
require only one positive power supply
voltage.
The two power supplies required for a linear Ic
are usually equal in magnitude + 15 V and –
15 V.
Different arrangement can be used to obtain
+ VCC and – VEE from single supply .
