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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

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

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Characteristics of an ideal Op Amp

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 = ∞

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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

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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

Analog or Digital Passive or Active Audio or Radio

Advantage of Active filters Gain and frequency adjustments No loading problem Cost

Most Commonly used Filters

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Oscillators

Introduction Type of Oscillators

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

Op-Amps and Linear Integrated circuits by Ramakant A. Gayakward

Operational amplifier Design and Applications by Tobey-Graeme-Huelsman

Integrated Electronics - Jacob Millman and Christos Hallkias

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Thank You