Operational Amplifiers

DefinitionIdeal op-amp

Pin configuration of op-ampIdeal Voltage Transfer Curve Of

Op-ampOpen Loop Configuration

& Its TypeDifferential op-amp

Inverting op-ampNon-inverting op-amp

Summing op-ampIntegrator

Applications

What is an Op-Amp?

An Operational Amplifier (known as an “Op-Amp”) is a device that is used to amplify a signal using an external power source.

Op-Amps are generally composed of:Transistors, Resistors, Capacitors

= + +

Ideal Operational Amplifier

i

o

Rohms;inputInfinite3.

0Rohms;outputZero2.

Again;loopopenInfinite1.

Ideal op-amp is characterized by:

4. Zero output voltage when input is voltage is zero.

5. Infinite CMRR.

Operational Amplifiers

inverting input

noninverting input

output

V-

V+

The basic op amp with supply voltage included is shown

in the diagram below.

Figure : Basic op amp diagram with supply voltage.

Pin configuration of op-amp

A typical one is the eight pin dual package.

The inverting input, pin 2.The non-inverting input, pin 3.The output, pin 6.The positive power supply V+, pin 7.The positive power supply V-, pin 4.

Fig : Op-amp pin configuration and circuit symbol

Ideal versus Real Op-Amps

Parameter Ideal Op-Amp Real Op-Amp

Differential Voltage Gain ∞ 105 - 109

Gain Bandwidth Product (Hz) ∞ 1-20 MHz

Input Resistance (R) ∞ 106 - 1012 Ω

Output Resistance (R) 0 100 - 1000 Ω

Ideal

Real

Ideal Voltage Transfer Curve Of Op-amp

Fig: Ideal voltage transfer curve

Open Loop Configuration

There are three open loop configuration of op-amp. They are :

i. Differential Amplifierii. Inverting Amplifieriii. Non-inverting Amplifier

Differential Amplifier

A difference amplifier is a device that amplifies the

difference between two inputs but rejects any signals

common to the two inputs.

Fig: The differential amplifier

Inverting amplifier

In the inverting amplifier only one input is applied and that

is to the inverting input terminal.

Fig: The inverting amplifier

In this configuration, the input is applied to the non-invertinginput terminals, and the inverting terminal is connected withground.It provides a positive voltage gain.

Non-inverting Amplifier

Fig: The non-inverting

amplifier

Summing Amplifier

The circuit shows a three-input summing amplifier circuit

which provided a means of algebraically summing three

voltages. Each multiplied by a constant gain factor.

For n inputs we will have, 𝑽𝟎 = −𝑹𝒇 × 𝒊

𝑽𝒊𝑹𝒊

𝑿𝑪 =𝟏

𝑱𝑾𝑪=𝟏

𝑺𝑪

Integrator

It is the feedback component used is a capacitor the resulting connection is called an integrator.

Fig: Integrator

AC and DC signals application

Digital-to-Analog converters

Analog computers

Active filters

Oscillators

Regulators

Rectifiers

Clippers etc.

Applications of Op-amp

Thanks

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