op amp intro

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ANALOG ELECTRONICS ANALOG ELECTRONICS II II EMT 212/4 EMT 212/4 Semester 1 2006/2007 Semester 1 2006/2007

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ANALOG ELECTRONICS IIANALOG ELECTRONICS II

EMT 212/4EMT 212/4

Semester 1 2006/2007Semester 1 2006/2007

SYLLABUSSYLLABUS

1. OPERATIONAL AMPLIFIER (OP-AMP) Operation Differential amplifier Common-mode Parameters Basic op-amp Practical op-amp Data sheet

2. APPLICATIONS OF OP-AMP AND FREQUENCY RESPONSE Summing amplifier Voltage follower Comparator Integrator Differentiator Frequency response Compensation

3. FEEDBACK CIRCUITS Concepts of feedback Types of feedback connection Practical feedback circuit Feedback amplifier

SYLLABUS (cont’d)SYLLABUS (cont’d)

4. OSCILLATOR Basic operating principles of an oscillator Phase-shift Wien bridge Crystal oscillator Uni-junction

5. ACTIVE FILTERS Basic filter Filter response characteristics Low-pass filter High-pass filter Band-pass filter Band-stop filter Frequency response measurement Design of filter: Butterworth, Chebychev, Elliptic

6. VOLTAGE REGULATOR Introduction Terminology Zener diode regulator Linear IC regulator Op-amp linear IC regulator

OPERATIONAL OPERATIONAL AMPLIFIERAMPLIFIER

(OP-AMP)(OP-AMP)

OP-AMP CONCEPTOP-AMP CONCEPT

HISTORYHISTORY

Fairchild

1964: The First Linear IC

The µA702 Op-Amp

12 Transistors

Designer: Bob Widlar

1965: A Best-Seller

The µA709 Op-Amp

14 Transistors

Designer: Bob Widlar

0.60 Inches

After Widlar left Fairchild, Dave Fullagar continued op-amp After Widlar left Fairchild, Dave Fullagar continued op-amp design and came up with the uA741 which is the most design and came up with the uA741 which is the most popular operational amplifier of all time.popular operational amplifier of all time. This design’s basic architecture is almost identical to This design’s basic architecture is almost identical to

Widlar’s 309 op-amp with one major difference: the Widlar’s 309 op-amp with one major difference: the inclusion of a fixed internal compensation capacitor. inclusion of a fixed internal compensation capacitor.

This capacitor allows the uA741 to be used without This capacitor allows the uA741 to be used without any additional, external circuitry, unlike its any additional, external circuitry, unlike its predecessors.predecessors.

The other main difference is the addition of extra The other main difference is the addition of extra transistors for short circuit protection.transistors for short circuit protection.

This op-amp has a gain of around 250,000This op-amp has a gain of around 250,000

HISTORY (cont)HISTORY (cont)

Inexpensive, efficient, versatile, and readily available building blocks for many applications Amplifier which has

Very large open loop gainDifferential input stageUses feedback to control the relationship between the input and output

WHAT IS AN OP-AMP?

WHAT DOES AN OP-AMP DO?WHAT DOES AN OP-AMP DO?

Performs many different “operations” Addition/SubtractionIntegration/DifferentiationBufferingAmplification

o DC and AC signals

x dt

dx

WHERE IS AN OP-AMP USED?WHERE IS AN OP-AMP USED?

Many applications including Comparators Oscillators Filters Sensors Sample and Hold Instrumentation Amplifier

INPUT STAGE

STAGES OF AN OP-AMPSTAGES OF AN OP-AMP

OUTPUT STAGE

GAIN STAGE

STAGES OF AN OP-AMPSTAGES OF AN OP-AMP

INPUT STAGEINPUT STAGE

Provides differential input for the op-amp Provides dc gain Has very high input impedance

Draws negligible input currento Enables user to utilize ideal Op-Amp equations for circuit analysis

GAIN STAGEGAIN STAGE

Provides the “gain” of the amplifier Gains up the differential signal from input and conveys it to the output stage

OUTPUT STAGEOUTPUT STAGE

Delivers current to the load Very low impedance output stage

To minimize loading the output of the op-amp May have short circuit protection

INPUTS OF OP-AMP & PACKAGESINPUTS OF OP-AMP & PACKAGES

DIFFERENTIAL INPUT MODEDIFFERENTIAL INPUT MODE

Both input terminals are usedBoth input terminals are used Input signals are 180º out of phaseInput signals are 180º out of phase Output is in phase with non-inverting Output is in phase with non-inverting

inputinput

INVERTING MODEINVERTING MODE

Non-inverting input is grounded Non-inverting input is grounded (connected to mid-supply)(connected to mid-supply)

Signal is applied to the inverting inputSignal is applied to the inverting input Output is 180º out of phase with inputOutput is 180º out of phase with input

NON-INVERTING MODENON-INVERTING MODE

Inverting input is grounded (connected to Inverting input is grounded (connected to mid-supply)mid-supply)

Signal is applied to the non-inverting inputSignal is applied to the non-inverting input Output is in phase with the inputOutput is in phase with the input

OP-AMPS: 741OP-AMPS: 741

We use real op-amps: 741We use real op-amps: 741Note the pin connections for the ICNote the pin connections for the IC

Note: Literally a Black Box

OP-AMP: 741OP-AMP: 741

Op-Amps require powerOp-Amps require power 741 requires plus and minus 15V741 requires plus and minus 15V Others may require only positive or Others may require only positive or

both positive and negative voltagesboth positive and negative voltages Output voltage is limited to Output voltage is limited to Usually filter capacitors are Usually filter capacitors are

connected to power to reduce noiseconnected to power to reduce noise

V V VCC OU T CC

OP-AMP 741(schematic)OP-AMP 741(schematic)

ICs come in many ICs come in many types of types of packages. We will packages. We will use the 8-pin, use the 8-pin, dual-in-line or DIP dual-in-line or DIP packagepackage

Note the other Note the other offset nulling offset nulling circuitcircuit

Data SheetData SheetLM741LM741

RF

RF

Data SheetData SheetLM741LM741

Data Data SheetSheetLM741LM741

Data SheetData SheetLM741LM741