1.operational amplifier

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03/07/15 Prof.Satheesh MB, INA, Ezhimala Operational-Amplifier and its Applications Course: 90 INAC-L&X AT-15 Prof.Satheesh Monikandan B [email protected]

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Page 1: 1.Operational Amplifier

03/07/15 Prof.Satheesh MB, INA, Ezhimala

Operational-Amplifier and its Applications

Course: 90 INAC-L&X

AT-15

Prof.Satheesh Monikandan [email protected]

Page 2: 1.Operational Amplifier

03/07/15 Prof.Satheesh MB, INA, Ezhimala

Outline

• Introduction • The 741 Op-Amp Circuit• The ideal Op Amp• The inverting configuration • The non-inverting configuration• Integrator and differentiator

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Introduction

• Analog ICs include operational amplifiers, PLL, etc.

• A complete op amp is realized by combining analog circuit building blocks.

• The bipolar op-amp has the general purpose variety and is designed to fit a wide range of specifications.

• The terminal characteristics is nearly ideal.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The 741 Op-Amp Circuit

• General description

• The input stage

• The intermediate stage

• The output stage

• The biasing circuits

• Device parameters

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

BLOCK DIAGRAM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

General Description

• 20 transistors, few resistors and only one capacitor

• Two power supplies

• Short-circuit protection

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

PIN DIAGRAM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

ARCHITECTURE

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Ideal Op Amplifier

Symbol for the op amp

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Ideal Op Amplifier

The op amp shown connected to dc power supplies.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Characteristics of the Ideal Op Amplifier

• Differential input resistance is infinite.• Differential voltage gain is infinite.• CMRR is infinite.• Bandwidth is infinite.• Output resistance is zero.• Offset voltage and current is zero.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Equivalent Circuit of the Ideal Op Amp

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

FREQUENCY RESPONSE

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

TRANSFER CHARACTERISTICS

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Inverting Configuration

The inverting closed-loop configuration.

Virtual ground.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Inverting Configuration

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Inverting Configuration

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Inverting Configuration

• Shunt-shunt negative feedback• Closed-loop gain depends entirely on passive

components and is independent of the op amplifier.

• Engineer can make the closed-loop gain as accurate as he wants as long as the passive components are accurate.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

I/O WAVEFORM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Non-inverting Configuration

The non-inverting configuration.

Series-shunt negative feedback.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Non-inverting Configuration

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

I/O WAVEFORM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Voltage follower

(a) The unity-gain buffer or follower amplifier.

(b) Its equivalent circuit model.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

I/O WAVEFORM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Weighted Summer

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

A Single Op-Amp Difference Amplifier

Linear amplifier.

Theorem of linear Superposition.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

A Single Op-Amp Difference Amplifier

Application of superposition

Inverting configuration

v o1=−R2

R1

v I1

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

A Single Op-Amp Difference Amplifier

Application of superposition.

Non-inverting configuration.

v o2=(1+R2

R1

)(R4

R4+R3v) I2

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Integrators

The inverting configuration with general impedances in the feedback and the feed-in paths.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

The Inverting Integrators

The Miller or inverting integrator.

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Frequency Response of the integrator

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I/O WAVEFORM

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The op-amp Differentiator

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The op-amp Differentiator

Frequency response of a differentiator with a time-constant CR.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

I/O WAVEFORM

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Bistable Circuit

The bistable circuit (positive feedback loop)

The negative input terminal of the op amp connected to an input signal vI.

v+=voR1

R1+R2=vo β

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Bistable Circuit

The transfer characteristic of the circuit in (a) for increasing vI.

Positive saturation L+ and negative saturation L-

V TH =L+ β

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Bistable Circuit

The transfer characteristic for decreasing vI.

V TL=L− β

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Bistable Circuit

The complete transfer characteristics.

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Application of Bistable Circuit as a Comparator

• Comparator is an analog-circuit building block used in a variety applications.

• To detect the level of an input signal relative to a preset threshold value.

• To design A/D converter.• Include single threshold value and two threshold

values.• Hysteresis comparator can reject the interference.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Application of Bistable Circuit as a Comparator

Block diagram representation and transfer characteristic for a comparator having a reference, or threshold, voltage VR.

Comparator characteristic with hysteresis.

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03/07/15 Prof.Satheesh MB, INA, Ezhimala

Application of Bistable Circuit as a Comparator

Illustrating the use of hysteresis in the comparator characteristics as a means of rejecting interference.

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Generation of Square Waveforms

The circuit obtained when the bistable multi-vibrator is implemented with the positive feedback loop circuit.