1. Department of CNET Electronic Circuit II
Chapter 1
Mohammed Abdul Gaffar

2. Amplifier strengthens the weak signal. I/p Signal o/p Signal
Amplifier Definition
Amplifier strengthens the weak signal.
I/p Signal o/p Signal
Amplifier

3. OPERATIONAL AMPLIFIER
An operational amplifier  (often op-amp or op amp) is a DC coupled high-gain electronic voltage amplifier.
Op-Amp primarily used to perform mathematical operations such as addition, subtraction, integration and differentiation.
Symbol
The OP-AMP always has two inputs and one output.
+Vcc & -Vee are the biasing voltages.

4. Operational Amplifers
Operational amplifiers (op-amps) are very high gain dc coupled amplifiers.
One of the inputs is called the inverting input (-);
The other is called the Noninverting input. (+)
Usually there is a single output.

5. Terminals

6. Internal Circuit of Op-Amp

7. Ideal And Practical Op-Amp
Ideal Op-Amp
Infinite gain.
Infinite input resistance.
Zero output resistance (order of 10’s of ohms)
Infinite bandwidth (practically restricted by slew rate).
Practical Op-Amp
Practically Gain is of the order of 10^5 and is a function of frequency. Gain decreases linearly with slope of 6db/octave, exhibits the characteristic of low pass filter with gain.
Input resistance is of the of mega ohm Order due to differential stage at the front end.
Output resistance order of tens of ohms.
Practically bandwidth of Op-amp restricted by slew rate.
Practical Op-amp exhibits offsets and non linearity.

8. Characteristics of Ideal op-amps Infinite voltage gain, ∞
The Ideal Op-Amp
Characteristics of Ideal op-amps
Infinite voltage gain, ∞
Infinite bandwidth, and
Infinite input impedance/Resistance.
In addition, the ideal op-amp has zero output impedance.

9. Finite gain or very large gain. Finite bandwidth or very high gain.
The Practical Op-Amp
Finite gain or very large gain.
Finite bandwidth or very high gain.
And Finite or very big input impedance,
Small output impedance.

10. Block Diagram
Internally, the typical op-amp has a differential input, a voltage amplifier, and a push-pull output. the differential amplifier amplifies the difference in the two inputs.

11. Points for OP-AMP Block diagram
Internally the OP-AMP has three amplifier stages.
The first stage is the Differential amplifier, it has two inputs and two outputs.
The second stage is Voltage amplifier also called as gain stage. It also has two inputs and two outputs.
The third stage is Push-Pull amplifier, which has two inputs and only one output.

12. Basic Differential Amplifier Input stage.
Circuit Diagram

13. Points about the Basic Differential Amplifier.
Basic Differential Amplifier is the first stage of the Operational Amplifier.
It has two inputs and two outputs.
It has the ability to amplify the difference of inputs.
If both the inputs are same the output will be zero.