APLICATIONS LINEAR AND DIGITAL INTEGRATED CIRCUITS Asst. … Digital... · 2019-09-23 · THERMAL DRIFT: ØBias current, ... HIGH FREQUENCY MODEL OF OPAMP. AC characteristics 17 Frequency

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LINEAR AND DIGITAL INTEGRATED CIRCUITS

APLICATIONS

Name : K.Sindhu

Asst. Prof..

UNIT-I

OP-AMPS

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ü An integrated circuit (IC) is a miniature ,low cost

electronic circuit consisting of active and passive

components fabricated together on a single crystal of

silicon.

üThe active components are transistors and diodes

and passive components are resistors and capacitors.

INTEGRATED CIRCUITS

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ü Advantages:

1.Miniaturization and hence increased equipment

density

2.Cost reduction due to batch processing

3. Improving the Functional performance

4.Matched devices

5. Increased operating speeds

6.Reduction in power consumption

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ü Integrated circuits offer a wide range application

and cloud be broadly classified as:

1.Digital ICs

2.Linear ICs

üBased upon the requirement , two distinctly

difference IC technology namely, Monolithic

technology and hybrid technology have been

developed

CLASSIFICATION

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üIn monolithic integrated circuits , all circuit

components both active and passive elements and

their interconnection are manufactured into or on top

of a single chip of silicon.

IC packages available

1. Metal can package.

2. Dual-in-line package.

3. Ceramic flat package.

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CIRCUIT SYMBOL ü The Circuit Schematic of an OP- amp triangle .

üIt has two input terminal and one output terminal .

üThe terminal with a( - ) sigh is called Inverting input terminal and

the terminal with (+) sigh called the non- inverting input terminal.

Inverting input terminal

+

Non – inverting input terminal

Output terminal

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THE IDEAL OPERTIONAL AMPLIFIER

ü OP – amp is said to be ideal if it has the following

characteristics.

Open loop Voltage again : AoL = Infinity

Input impedance : Ri = Infinity

Output Impedance : Ro = 0

Band width : BW = infinity

zero offset i.e. v0=0 when v1 =v2=0

Basic processes involved in fabricating Monolithic ICs

1. Silicon wafer (substrate) preparation2. Epitaxial growth3. Oxidation4. Photolithography5. Diffusion6. Ion implantation7. Isolation technique8. Metallization9. Assembly processing & packaging

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OPERATION AMPLIFIER

• An operational amplifier is a direct coupled high gain amplifier

consisting of one or more differential amplifiers, followed by a

level translator and an output stage.

• It is a versatile device that can be used to amplify ac as well

as dc input signals & designed for computing mathematical

functions such as addition, subtraction ,multiplication,

integration & differentiation

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DC characteristics

Input bias current:

Input bias current IB as the average value of the base currents

entering into terminal of an op-amp. IB=(IB

+ + IB- )/2

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DC characteristics

Input offset voltage :

Ø A small voltage applied to the input terminals to make the

output voltage as zero when the two input terminals are

grounded is called input offset voltage

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DC characteristics

Input offset current :

• The difference between the bias currents at the input

terminals of the op- amp is called as input offset current.

• The input terminals conduct a small value of dc current to bias

the input transistors.

• Since the input transistors cannot be made identical, there

exists a difference in bias currents

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DC characteristics

THERMAL DRIFT:

Ø Bias current, offset current and offset voltage change with

temperature.

Ø A circuit carefully nulled at 25oc may not remain so when the

temperature rises to 35oc. This is called drift.

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AC characteristics

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Frequency Response

HIGH FREQUENCY MODEL OF OPAMP

AC characteristics

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Frequency Response

OPEN LOOP GAIN VS FREQUENCY

Need for frequency compensation in practical op-amps

• Frequency compensation is needed when large bandwidth

and lower closed loop gain is desired.

• Compensating networks are used to control the phase shift

and hence to improve the stability

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Slew Rate

• The slew rate is defined as the maximum rate of change of

output voltage caused by a step input voltage.

• An ideal slew rate is infinite which means that op-amp’s

output voltage should change instantaneously in response to

input step voltage

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BASIC Op-amp symbol

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Non-inverting input

inverting input

0utput

+5v

-5v

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Inverting Op-Amp

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• Assume an IDEAL OP-AMP,AS Vd=0,node ‘a’ is at ground potential and the current i1 through Rin is

I1=vin/Rin

• Output voltage,

Vo=-i1 Rf=-vin(Rf/R1)

• Gain

A(CL)=vo/vin=(-Rf/Rin)

• Nodal equation at node ‘a’ is

(Va-vin)/RIN+(va-vo)/Rf=0

• Since va=0,

A(CL)=vo/vin=(-Rf/Rin)

Non-Inverting Amplifier

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• Rf and R1 Potential divider

Vi=vo(R1/(R1+Rf))

• No current flows into the op-amp

Vo/vi=(R1+Rf)/R1

=1+(Rf/R1)

• Voltage gain,

ACL=vo/vi=1+(Rf/R1)

Voltage follower

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If Rf=0 and R1=infinity

Differential amplifier

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Differential amplifier

• This circuit amplifies only the difference between

the two inputs.

• In this circuit there are two resistors labeled

R IN Which means that their values are equal.

• The differential amplifier amplifies the difference of

two inputs while the differentiator amplifies the

slope of an input

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Instrumentation Amplifier

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Instrumentation Amplifier

• In a number of industrial and consumer applications, the

measurement of physical quantities is usually done with the

help of transducers.

• The output of transducer has to be amplified So that it can

drive the indicator or display system.

• This function is performed by an instrumentation amplifier.

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Features of instrumentation amplifier

1. high gain accuracy

2. high CMRR

3. high gain stability with low temperature co-

efficient

4. low dc offset

5. low output impedance

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Differentiator

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Integrator

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Summer

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Comparator

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Comparator

• A comparator is a circuit which compares a

signal voltage applied at one input of an op-

amp with a known reference voltage at the

other input.

• It is an open loop op - amp with output + Vsat

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Applications of comparator

1. Zero crossing detector

2. Window detector

3. Time marker generator

4. Phase detector

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Schmitt trigger

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Schmitt trigger

• Schmitt trigger is a regenerative comparator.

• It converts sinusoidal input into a square wave output.

• The output of Schmitt trigger swings between upper

and lower threshold voltages, which are the reference

voltages of the input waveform

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Voltage regulator:

• The purpose of a voltage regulator is to maintain a constant

voltage across a load regardless of variations in the applied

input voltage and variations in the load current.

• 1. 723 voltageregulator

2. Three terminal voltage regulator

• The 723 regulator can give adjustable output voltage in a wide range.

• provides short circuit protection and current foldback using external components