What is the Difference Between Amplifier and Operational Amplifier (Op-Amp)?
In electronic circuits and devices, amplifiers are frequently used to increase the power of a signal. An amplifier is an electronic circuit that increases the power of an electrical signal. It is used in power electronics, telecommunication, signal processing, audio system, etc.
Amplifiers and operational amplifiers can both amplify an electrical signal, there is no doubt about it. As a matter of fact, Amplifier is a general term and operational amplifier is a type of amplifier. But they are very different in structure, functions, configurations, etc. This article briefly explains all the differences.
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Amplifier
An amplifier is an electronic circuit that helps in increasing the power of an electrical signal using an external power. The electrical signal can be either a voltage signal or a current signal. It has a single input terminal and single output terminal having high input impedance and low output impedance. There are no feedback loops. They are commonly used in audio systems, power supplies, signal possessing, etc.
The amplifiers are classified into several types based on their performance such as class A, class B, class AB, class C, class D, etc. They are classified due to their function and application.
An amplifier is defined by certain parameters such as gain, frequency response, bandwidth, feedback, power consumption, input and output impedance and noise, etc.
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Operational Amplifier
An operational amplifier or Op-amp is a type of amplifier used in electronic circuits that has a very high gain. It is used to perform several mathematical operations such as sum, difference, and compare two different signals. It has two input terminals, inverting and non-inverting input terminals. Therefore it can be configured in either inverting or non-inverting operations.
Ideally, op-amp has infinite input impedance and zero output impedance with infinite gain. There is a feedback loop that is used to feed back the output signal through a combination of resistor and capacitor. It allows it to be used in various configurations such as comparator, differentiator, integrator, amplifier, etc.
One key difference between an amplifier and an operational amplifier is that op-amp has a very high input impedance allowing it to be used in circuits with high impedance. On the other hand, amplifiers have relatively low input impedance which can cause a loading effect.
Another key difference is that op-amp has a very low output impedance of around a few ohms. Therefore, it can be directly connected to the load circuit without the need for any buffer circuit. Whereas an amplifier has a relatively higher output impedance thus it requires a driver circuit such as a buffer amplifier to drive a load.
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Difference between Amplifier and Operational Amplifier
The following table shows the comparisons between Typical amplifier and OP-AMP.
| Amplifier | Operational Amplifier |
| It is an electronic circuit that increases the power of an electrical signal. | It is an electronic device that amplifies as well as performs several mathematical operations such as addition, subtraction, integration, etc. on a signal. |
| It has only one input terminal | It has two input terminals; inverting input and non-inverting input. |
| It has low input impedance compared to op-amp. | It has a relatively large input impedance. |
| It has a large output impedance compared to the op-amp. | It has a relatively very small input impedance. |
| It has only one external power supply. | It can have more than one external power supply. |
| It has a limited and fixed gain. | It has a very high gain in the range of thousands. |
| There are no feedback loops. | It is almost always connected in a feedback configuration. |
| Amplifiers have a very fast response time. | Op-amp has a very fast response time. |
| It generates noise in the electrical system. | The op-amp has comparatively low noise. |
Comparison Between Amplifier & OP-Amp
Gain
The gain is the ratio of the output signal to the input signal.
Amplifiers have a fixed gain that cannot be adjusted. It is limited to a certain value which makes them able for certain applications.
Op-amp has a very high gain which can be adjusted with the help of a resistor network. Thus the signal can be amplified according to need.
Configuration
Amplifiers can be used in different configurations such as common-emitter, common-base and common collector. Each configuration provides a different gain and input/output impedance.
In op-amp, there are several configurations such as inverting, non-inverting, summing, integrating, differentiating amplifiers, etc.
Input and Output
The amplifier has only one input and one output terminal.
Op-amp has two input terminals where one of them is inverting input and the other is a non-inverting input terminal. It has one output terminal that is feedback into the op-amp for adjustable gain.
Input Impedance
Amplifiers have different input and output resistance depending on their configuration. However, in every configuration, an amplifier has a lower input impedance than an operational amplifier. and It has a larger output impedance than op-amp.
It means op-amp takes no to little input current and its output voltage is not affected by the load circuit.
Power Supply
Amplifiers require an external power supply that determines the maximum output voltage is the signal. Whereas op-amp has a wide range of operating voltages including the use of two or more than two power supplies at a time.
Feedback
Amplifiers do not use a feedback loop whereas op-amp is always used in feedback configuration.
Response Time
The amplifier has a fast response time as compared to an op-amp.
Noise
Noise is the unwanted signal that is added to the original signal causing misinformation and error in it. Amplifiers generate more noise as compared to op-amps.
Applications
Amplifiers are only used for the amplification of the signal in power supplies, signal processing and audio systems, etc. Whereas op-amp is specially used for mathematical operations such as addition, subtraction and comparison of signal, etc.
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