Basics of Operational Amplifier
Operational amplifier, also called operational amplifier, is an integrated circuit, which can be used to perform direct coupled high gain amplifier . You can use the opamp with both AC and DC signals. This chapter discusses the characteristics and types of operational amplifiers.
Construction of an operational amplifier
An operational amplifier consists of one or more differential amplifiers, a level translator and an output stage . A differential amplifier is present at the input stage of an operational amplifier, and therefore an operational amplifier consists of two input terminals . One of these terminals is called inverter terminal and the other is calledé noninverting terminal . The terminals are named according to the phase relationship between their respective inputs and outputs.
Operational Amplifier Specifications
The important characteristics or parameters of an operational amplifier are as follows 
 Open loop voltage gain
 Output offset voltage
 Common mode rejection rate
 Slew rate
This section describes these characteristics in detail as shown below 
Open Loop Voltage Gain
The open loop voltage gain of an amp op is its differential gain without any feedback path.
Mathematically, the open loop voltage gain of an op amp is represented by 
$$ A_ {v} = frac {v_0} {v_1v_2} $ $
Output offset voltage
The voltage present at the output of an opamp whene its differential input voltage is zero is called voltage output offset.
Common mode rejection rate
The common mode rejection rate ( CMRR ) of an opamp is set as the ratio o of the differential closed loop gain, $ A_ {d} $, and the common mode gain, $ A_ {c} $.
Mathematically, CMRR can be represented by 
$ $ CMRR = frac {A_ {d}} {A_ {c}} $$
Note t Each common mode gain, $ A_ {c} $ of an op amp is the ratio of the common mode output voltage to the common mode input voltage.
Slew Rate
Slew Rate of an opamp is defined as the maximum rate of change in the output voltage due to a step input voltage.
Mathematically, the scan rate (SR) can be represented by 
$$ SR = Maximum: of: frac {text {d} V_ {0}} {text { d} t} $$
Where, $ V_ {0} $ is the output voltage. In general, theslew rate is measured in $ V / mu: Sec $ or $ V / m: Sec $.
Types of operational amplifiers
An opamp is represented by a triangular symbol with two inputs and one output.
Opamps are of two types: ideal opamps and practical opamps .
They are discussed in detail as shown below 
Ideal op amp
An ideal op amp exists only in theory, and practically does not exist. The equivalent circuit of an ideal op amp is shown in the figure below 
An ideal opamp has the following characteristics 

Input impedance $ Z_ {i} = infty Omega $

Output impedance $ Z_ {0} = 0 Omega $

Sheath open loop voltage $ A_ {v} = infty $

If (the voltage(differential input) $ V_ {i} = 0V $, then the output voltage will be $ V_ {0} = 0V $

The bandwidth is infinite . This means that an ideal op amp will amplify signals of any frequency without any attenuation.

The common mode rejection rate (CMRR) is infinite .

The (SR) sweep speed is infinite . This means that the ideal op amp will instantly produce an output change in response to a step input voltage.
Practical operational amplifier
In practice, operational amplifiers are not ideal and deviate from their ideal characteristics due to certain imperfections in the operation. of manufacturing. The equivalent c circuit of a practical op amp is shown in the following figure 
A practical opamp has the following characteristics 

Input impedance, $ Z_ {i} $ of the order of Mega ohms .

Output impedance, $ Z_ {0} $ on the order of a few ohms. .

Open loop voltage gain, $ A_ {v} $ will be high .
When choosing a practical op amp, you should check whether it meets the following conditions 

The input impedance , $ Z_ {i} $ should be as high as possible.

The output impedance, $ Z_ {0} $ should be as low as possible.

Open loop voltage gain, $ A_ {v} $ should be as high as possible.

The output offset voltage should be as low as possible.

The operating bandwidth should be as high as possible.

CMRR should be as high as ppossible.

The scanning speed should be as high as possible.
Note  The IC 741 op amp is the most popular and convenient op amp.