understanding operational amplifier

Hi

Please note that I'm a beginner so please keep your replies simple and straightforward so that you could be understood and your effort fully appreciated. Thank you.

1: Why is operational amplifier or op-amp so called? Is there also something like non-operational amplifier?

2: As I see it operational amplifier could be modified to do different things with the input signal. For instance, it could be designed into an inverting amplifier, non-inverting amplifier, etc.

3: Is a simple oscillator also made from an op-amp?

4: Can you please provide me some link which shows me in images that how different type of amplifier, such as inverting amplifier or differential amplifier, affects the input signal? The Wikipedia page only gives math formulas.

Thank you very much for your help and time.

Best wishes
PG

WHY it is called Operational Amplifier:

1. it is an amplifier
2. you do mathematical "OPERATION" with it; // i.e: addition, multiplication etc.

Oscillator:
you can use Vacuum tube to built oscillator // assuming there is no transistor in your planet

As XT.5155 said, an op-amp is an operational amplifier. It amplifies signals while performing some operation. Generally, this is a voltage multiplication (also called gain). If you build an op-amp with a gain of 2, then for a given input voltage, the output voltage will be 2x the voltage of the input.

For a pile of op-amp circuits, keep a copy of AN-31 handy (get it from national.com, HERE)

Here's a nice little tutorial to give you some practical insight into the inverting op-amp, the easiest circuit to understand.
Inverting Op Amp

Some higher-level discussion on how the various op-amp circuits work (inverting, non-inverting, summing amp, etc).
Op-amps - The Inverting Amplifier

Hi PG1995,

here is one recommendation from my side:
With the aim to understand the fundamental meaning as well as the function principle of opamps it is absolutely necessary to understand the concept of negative feedback.
Without feedback the opamp is completely useless.
The main features of opamps are
*the voltage gain approaching infinity (in practice: 1E4...1E5, it is a voltage amplifier with high input and very low output impedances). As a result the desired gain properties are determined by the feedback network only!
* For +/- double supply voltages) the input and output quiescent potentials are zero. Thus, the opamp is an amplifier from dc to an upper frequency limit and there is no need for coupling capacitors - are very important property.

Finally, one remark to oscillators. Oscillators are active circuits that need a certain amount of gain (for compensating unavoidable losses within the frequency determining network). In principle, each type of amplifier (voltage, current or in combination) can be used for this purpose. But the circuits look different and some are more convinient than others.

Hi,
In short:
An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp produces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals.
Yes there are non-operational amplifiers, too (saying all in brief). Below is a link which can give you an extended lessons on OP-AMPS.
How does an op amp work? How do I use an op amp? | Chris Gammell's Analog Life
Hope it helps.

Thank you very much, everyone. I genuinely appreciate your help and effort to educate me about op-amp.

1: A op-amp can be modified to do different things. For instance, it could be modified into a summing amplifier who does addition. But, is there anything in itself such as op-amp? What does it do? Or, is it simply a catch all term for all related amplifiers such as differential amplifier, summing amplifier, etc.?

2: Are there other kinds of amplifiers besides op-amp?

3: I have always been under the impression that an amplifier is used to amplify voltage. Can an amplifier also be used to amplify current?

4: The word 'feedback' simply suggests something that is returned to a machine, system, or process to improve output. I have seen in some circuits that a wire connects the output of the amplifier with one of its input and I presume it's called feedback. How would you explain this feedback and its use? Please keep it simple.

1: A op-amp can be modified to do different things. For instance, it could be modified into a summing amplifier who does addition. But, is there anything in itself such as op-amp? What does it do? Or, is it simply a catch all term for all related amplifiers such as differential amplifier, summing amplifier, etc.?

Click to expand...

An op amp is a differential amplifier circuit made of of multiple transistors. This basic device can be modified to perform a particular task by adding resistors, caps, and inductors around it in specific configurations, depending on the task you want it to perform. For instance, two resistors can make it into an inverting amplifier with user-selectable gain. Add another resistor, and you can make a non-inverting amplifier. Add a capacitor, and you can make a voltage integrator.... the list is extensive. See the App Note I pointed to earlier for the many circuits that you can build, using an op-amp as the basic building block.

2: Are there other kinds of amplifiers besides op-amp?

Click to expand...

An op-amp is actually a collection of several different circuits, including amplifiers and current mirrors (simple transistor-based circuits). A very basic (fundamental) amplifier is constructed using a single transistor. For more information, fire up your favorite search engine (or search on here) for Class A amplifiers. Simple transistor amplifiers are the fundamental building blocks of all the electronic circuits we use today. The two major ways that a transistor is used are: as an amplifier, or as a switch (on/off).

Here's what's inside a 741 operational amplifier: **broken link removed**

3: I have always been under the impression that an amplifier is used to amplify voltage. Can an amplifier also be used to amplify current?

Click to expand...

Yes, kinda... it's not quite like what you might be thinking of knowing what an op-amp is, but search for current-mode amplifiers. This is a higher-level subject than I think we should get into in this conversation. Once you get past class A amps and start looking at other non-linear types, you will see current-mode amplifiers show up. You can set up an op-amp to convert a current signal into a voltage, but that's not the 1:1 correlation that you originally asked about.

4: The word 'feedback' simply suggests something that is returned to a machine, system, or process to improve output. I have seen in some circuits that a wire connects the output of the amplifier with one of its input and I presume it's called feedback. How would you explain this feedback and its use? Please keep it simple.

Click to expand...

Feedback is a general term used in system design. The op-amp, and it's surrounding circuits, can be considered a system. This system can be expressed as a series of simple equations that define output voltage, based on the input voltage and the output voltage (thus feedback... some of the output voltage is sent back to modify the input voltage).

For a simple way to understand how an op-amp works, it always tries to make the + and - inputs stay at the same voltage, by changing the output voltage. Let's say you set up the circuit as a simple inverting op-amp. You apply 0 volts to the + input. Assume that the input resistor and feedback resistor are both 1Kohm. If you apply +1V to the input resistor, then the output of the circuit will go to -1V. Why?

Remember that the op-amp will change the output voltage so that the + and - inputs are the same voltage. If + is 0V, then - must also become 0V. If you have 1V at the input resistor, then some quick calculations with Ohms law (V=I*R) will tell you than the output voltage must be -1V, so that the - input is 0 volts. One thing to keep in mind, when solving equations around an op-amp, you assume that the input pins have zero current going into, or out of, them.

If I may ask a question, would an OP-AMP considered as analog computer.

Hello PG1995,

may I give you one single recommendation?
From your questions I can see that you really are a beginner in analog electronics. Fine, that you are interested in this challenging subject.
It is really challenging - and therefore, I am convinced it is by far not sufficient to ask some specific questions here in the forum. And your desire: "keep it simple" is hard to fulfill.
For this reason: Believe me, try to get a good elementary book on fundamentals of analog electronics and study the function of basic elements and circuits - including the principle of negative feedback.
Otherwise you will get lost in the "ocean" of question and answers. Each answer will cause a new question on your side - and such a forum like this certainly is not the right place to teach electronics from the beginning.
Sorry and regards
LvW

yes... it is better you read some basics materials like these
**broken link removed**

for the noise theory analysis of an operational amplifier here is a great term paper
Technology World: OPERATIONAL AMPLIFIERS Noise Theory

PG1995 said:

1: But, is there anything in itself such as op-amp? What does it do? Or, is it simply a catch all term for all related amplifiers such as differential amplifier, summing amplifier, etc.?

Click to expand...

An op amp is useless without support circuitry because of the incredibly high gain in open loop mode. An op amp is an idealized amp that can be used to create many different amp circuits depending how the support circuitry is designed.

PG1995 said:

2: Are there other kinds of amplifiers besides op-amp?

Click to expand...

Many: video amps, audio amps, IF amps, Bandpass/LowPass/HighPass amps, Class A,B,C,D,etc.... amps...........

PG1995 said:

3: I have always been under the impression that an amplifier is used to amplify voltage. Can an amplifier also be used to amplify current?

Click to expand...

Yes, an inverting current feedback amp. The input signal drives the inverting input and the negative feedback is used. The non-inverting input is grounded or DC reference.

PG1995 said:

4: I have seen in some circuits that a wire connects the output of the amplifier with one of its input and I presume it's called feedback. How would you explain this feedback and its use? Please keep it simple.

Click to expand...

Without feedback an op amp is useless as an amplifier because it is unstable due to the high open loop gain. Negative feedback is used to control the gain, bandwidth, distortion and output voltage offset of the amplifier. Positive feedback could be used for a Schmidt Trigger or to create an oscillator. No feedback or open loop circuit could be used as a comparator. Note: the feedback can be 'a wire', resistance, reactant, or impedance feedback. Generally, except as a voltage follower or buffer, only a portion of the output is fed back.