EEVblog #600 - OpAmps Tutorial - What is an Operational Amplifier?

The most often requested video! In this tutorial Dave explains what Operational Amplifiers (OpAmps) are and how they work. The concepts of negative feedback, open loop gain, virtual grounds and opamp action. The comparator, the buffer, the inverting and non-inverting amplifiers, the differential amplifier, and the integrator circuit configurations are also explained.
Then a practical breadboard circuit to demonstrate a virtual ground and the effect of voltage rail limitations.
All EEVblog Opamp related videos are here:

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[regal_]

I know this will probably get lost in the comments but I have to say it. I absolutely have a high respect for people like you who share knowledge so freely and willingly. People like you are a godsend. Thank you sincerely.

[mikaelmrup]

Six years later, this is still the best and most understandable intro to Op Amps ever.

[neilalbaugh]

As a retired Senior Applications Engineer at Burr-Brown and Texas Instruments, I must compliment you on this presentation! It is very similar to the "factory" technical presentations that we used to give to audiences around the globe. The technical level is just right, not to basic and not too advanced. Good job! To be a good teacher it takes far more than just knowledge of the subject. A teacher's job is to impart knowledge to his student; if the student doesn't understand, the teacher is not doing his job. Some PhDs can teach, others can't- Richard Feynman was an example of a fellow who not only thoroughly understood his subject but who could teach it as well.... and do it in an interesting and entertaining manner.

[kevinjad]

In my whole electronics major shit, I have never seen a person who explains virtual ground like this.
#RESPECT

[RRClassicman]

I Learned more in 10 min of your video than 1 month of my Power Control Electronics class. Thank

[mirkomueller]

what makes you a gorgeous teacher is that you not only talk about what is going on but also about what the follower might think is going on but actually is not and why. i had so many frustrating experiences in the past because of teachers that did'nt care about that. i truly love your lessons.

[berre]

5.300 students are very grateful you uploaded this video

[ashenjiang]

Eight years later, this is still the best and most understandable intro to Op Amps ever.

[jaguarpaw]

this video got me my first electronic job i watched this video before my interview and they quizzed me on op amps! the luck!

[tareksaglan]

Regarding the puzzle at the end, the low resistance effect is an increased current at the OA output. the OA at approximately Vout= -0.5V should sink 50uA which is higher than the value in the datasheet/figure13 of 30uA max. so the virtual ground voltage fluctuates and so does the output at approx. -0.5V.

[MarkJay]

"The gain is almost infinite"

spoken like a true engineer!

[IamDerick]

Been a tech for 43 years and I have never seen it explained so concise. Thanks and I am turning the junior techs onto this video. Cheers!

[keithminchin]

I find myself revisiting this tutorial as a refresher every time I need to incorporate an OpAmp into one of my projects. Thanks Dave! 👍🏻

[bartekdudek]

Watched this 6 years ago as a teenage geek. Learned a lot. Now I rewatch as a 3rd year university student. Still useful. Gonna pass the exam today

[funkyironman]

If anyone is interested the gain of the non-inverting config can be derived from the voltage divider equation:

Vin = Vout*R1/(R1+Rf)
Vin/Vout = R1/(R1+Rf)
Vout/Vin = (R1+Rf)/R1
Vout/Vin = 1+Rf/R1

And the gain of the inverting config can be found from the currents:

I(Rf) = Vout/Rf
I(R1) =  -Vin/R1
-> Current through both resistors is equal so...
-Vin/R1 = Vout/Rf
Vout/Vin = -Rf/R1


:)

[RossPotts]

Interestingly I just recently recommended someone to look into using an opamp for their project...

EEVblog never disappoints.

[timoliver]

Hi dave I've been watching your channel a lot for the last couple years now and it's fantastic! I'm currently doing my honors in electronics engineering and my University here in hamilton New Zealand has instructed my class to watch this video on the current section we are covering on op-amps. You have finally made it to university level teaching my friend!

[Stelios.Posantzis]

Most excellent basic introduction to op-amps I know of. It tells you everything you need to know about fundamental operations of op-amps to get you on your way to understanding more complex circuits.

[rithanipriyanka]

Read this after 12:23 and listen to buffer amplifier again.
The primary objective of buffer circuit is to boost the current in any circuit at any stage. Buffer circuits are mainly used where a signal has very low current input(high input impedance) which needs to be increased maintaining the same voltage levels. So, this buffer circuits draws current from power source and adds it to the signal.

Buffer amp is also called as voltage follower or unity gain amplifier . Hope this makes sense now !

[flashUSA]

Very helpful. I'm an electronics technician and you see this stuff when you're doing repairs or troubleshooting but you never get down to the nitty gritty details especially after 30+ or so years goes by from your initial electronics training so it was really nice of you to explain this especially on layman's terms. Someone else mentioned in this blog about cutting and pasting working circuits into projects and calculating as you went along to fit your needs which is pretty much what I've done in the past so this has really been a BIG help in the memory refresh department. Thank you ten times over and may the "electro" Gods shine good fortune down upon you sir!