differential amplifiers

LINEAR INTEGRATED CIRCUITS AND

APPLICATIONS [MTE 2104]

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References:

1. Choudhary Roy D.,Shail B. Jain, “Linear Integrated Circuits”, Wiley Eastern, 2003

2. Stanley William D., “Operational Amplifiers with Linear Integrated Circuits”, Prentice Hall, 2004

3. Franco Sergio, “Design with Op-Amps and Analog Integrated Circuits”, McGraw Hill, 2002

4. Ramakant A. Gayakwad, “Op-Amps and Linear Integrated Circuits”, Prentice Hall India, 2000

5. Robert F. Coughlin and Fredrick F. Driscoll, “Operational Amplifiers and Linear Integrated Circuits”, PHI/Pearson, 2009

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Introduction to analog system design

• Analog signals are continuous in both time and value.

• Digital signals are discrete in time and value.

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Comparison element Analog signal Digital signal

Analysis Difficult Possible to analyze

Representation Continuous Discontinuous

Accuracy More accurate Less accurate

Storage Infinite memory Easily stored

Subject to Noise Yes No

Recording TechniqueOriginal signal is preserved

Samples of the signal are taken and preserved

Examples Human voice e.t.c Computers e.t.c

Comparison between analog and digital signals:

Analog signal can be depicted using three properties:

Amplitude

Frequency

Phase

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Integrated circuits(IC’s)

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IC’s An integrated circuit (IC), sometimes called a

chip is a semiconductor wafer on which

thousands or millions of tiny resistors,

capacitors, and transistors are fabricated.

Two main advantages of IC’s:

– cost and performance.

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Types of IC’s

• Linear IC: Linear ICs have continuously

variable output that depends on the input signal

level.

• Digital IC: Digital ICs operate at only a few

defined levels or states, rather than over a

continuous range of signal amplitudes.

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Applications of LICA

• Power amplifiers

• Operational amplifiers

• RF and IF amplifiers

• Voltage comparators

• Multipliers

• Radio receivers

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Advantages and disadvantages of analog systems

Advantages: Produces a more 'faithful' reproduction of the physical

quantity. make good use of bandwidth- they have power to define

infinite amount of data. No aliasing No quantization noise Analog signal processing can be vastly more simple than a

DSPDisadvantages: Noise and distortion problems Signal cannot be transmitted over long distances. Analog signals require hardware receivers and transmitters

that are designed to perfectly fit the particular transmission. 10

• Resistance:Resistance can be defined as the characteristic of a

medium that opposes flow of current through itself.

Unit:Ω

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• The current (I) through the resistor (R) is

defined as:

I=V/R

V=I.R

R=V/I

Basics:

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The power (P) dissipated in (R) is defined as:

P=I.V

P=V2 /R

P=I2 .R• Ex: calculate the value of resistance that will

result in 10 Watts with 10 Volts applied to the circuit shown in below fig.

• Solution: use P=V2 /R or R= V2 /P

Answer:R=10 Ω

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• Voltage Divider Calculation:Req= R1 + R2

V1 =R1.I and V2 =R2.I

I=Vin/ Req

Vin= V1+ V2

Vin=I.( R1 + R2)

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To calculate the output voltage :

V2=Vout=I.R2

Vout= R2.Vin / Req

Vout = Vin.R2 /( R1 + R2)

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Amplifiers• An amplifier or electronic amplifier is an

electronic device that increases the power of

a signal.

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• Three different kinds of amplifier gains are:

Voltage Gain ( Av )

Current Gain ( Ai )

Power Gain ( Ap )

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in

outi I

IntInputCurreentOutputCurrAnCurrentGai

ivp xAAAPowerGain

in

outv V

VgeInputVoltaageOutputVoltAnVoltageGai

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Voltage Gain in dB: av = 20 log Av

Current Gain in dB: ai = 20 log Ai

Power Gain in dB: ap = 10 log Ap