Basics Of Operational Amplifier

Operational Amplifier Tapan Kumar Jain

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Analog Electronics Syllabus

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Why is it called Op Amp?

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Operational Amplifier An Op-Amp is a direct coupled high gain amplifier usually consisting of one or more differential amplifiers and usually followed by level transmitter and an output stage.

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Internal Model of Real Op Amp

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Zin Input Impedance (very large ~ 2 MΩ) Zout Output Impedance (very small ~ 75 Ω) Aol Open-loop gain 07/12/09

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Characteristics of an ideal Op Amp     

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Input Resistance Zi = ∞ Output Resistance Zo= 0 Voltage Gain A = ∞ Bandwidth = ∞ Perfect balance i.e. Vo = 0 when V1 = V2 Characteristics do not drift with temp CMRR and Slew Rate = ∞ 07/12/09 6

Op amp with Feedback Amplifiers    

Voltage-series feedback Voltage-shunt feedback Current-series feedback Current-shunt feedback

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Voltage series feedback amplifier

•Negative feedback •Closed loop voltage gain •Input resistance with feedback •Output resistance with feedback •Bandwidth with feedback 07/12/09

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Applications of Op Amp     

Summing, scaling and averaging Instrumentation Integrator and Differentiator Log and Antilog Multiplier and Division

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Active filters 

Filter classification   

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Advantage of Active filters   

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Analog or Digital Passive or Active Audio or Radio Gain and frequency adjustments No loading problem Cost

Most Commonly used Filters

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Oscillators  

Introduction Type of Oscillators   

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Phase shift oscillators Wien bridge oscillators Quadrature oscillators

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Wave generator   

Square wave generator Triangular wave generator Saw tooth wave generator

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References 

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Op-Amps and Linear Integrated circuits by Ramakant A. Gayakward Operational amplifier Design and Applications by Tobey-GraemeHuelsman Integrated Electronics - Jacob Millman and Christos Hallkias 07/12/09

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Thank You

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