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A tutorial on the basics of an inverting and non-inverting summing amplifier using an op amp. The video assumes a basic knowledge of how inverting and non-inverting amplifiers using op amps work. If you are unfamiliar with this, I'd recommend viewing my video on how to easily understand the operation of most opamp circuits:
• #75: Basics of Opamp c...
or Dave Jones (EEVBlog)'s video on op amp basics:
• EEVblog #600 - OpAmps ...
The theory is presented, and measurements are made on the bench using the same circuit configurations shown in the theory. The circuit on the bench is based on an LM358 op amp powered off of a +/-15V split power supply. The analysis of this circuit is done using superposition (en.wikipedia.org/wiki/Superpos...)
A copy of the notes in the video can be found here:
www.qsl.net/w/w2aew//youtube/O...

Опубликовано:

30 июл 2024

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Комментарии : 79

@theovannieuwenhuizen5756 Год назад

Great explanation of summing amplifier. I'm here brushing up on old knowledge 😀 Very much like the way you explain and show how electronic circuits operate. 👍

@billmoran3812 7 лет назад

Great tutorial! Op-amps have always been kind of a mystery to me. Seeing their uses in practical circuits makes it easier to understand. One of the things I really like about the videos is being to view them multiple times if necessary to fully grasp the concepts.

@SatyajitRoy2048 8 лет назад

Its such a clear explanation about how it works and very good demonstration as well. All of your videos on fundamental theories are very informative and clear the things up at one go. Keep up the good work.

@SimpleEnough2k9 10 лет назад

Thanks Allan for the video. Opamps are very interesting little beasts to work/play with and they can be used for a LOT of applications. You and Dave covered some of the opamp topics in a friendly way, making the overall theory more accessible to us, therefore we can manage to create basic circuits and validate what's going on. Once again, thank you very much for your good work and taking the time to share your expertise with us. Dan.

@richardgarrett3188 10 лет назад

I still have my HP-15C calculator too! I bought it back in 1987 when I was going to the Naval Nuclear Power School. It was great because no one would ask to borrow it more than once because of the way you did calculations. LOL

@FirstWizardZorander 10 лет назад

Thanks a lot for this video. It's very satisfying to actually see the added waveforms on the scope. I really like your methodical approach, especially since I'm still a beginner.

@Drekkag 7 лет назад

Another great job of informing us. Got a lot of incite into op amps now thanks to you. Now I can experiment and play even more than resistors, capacitors, inductors, and transistors. I look forward to watching more of your videos. Thank you for all you are doing to help us who want more technological learning. 73, ad0am

@byronwatkins2565 3 года назад

First, you always must either use the voltage actually observed at the resistor or add the source impedance to that resistance. This is true for both the inverting and non-inverting cases. Second, the general non-inverting case is V+ = sum(V_i/R_i) / sum(1/R_i) applied to the non-inverting terminal. In this case R_i MUST include the series source impedances and V_i are the Thevenin voltages. We still get a weighted average; however, the current flowing in must also flow back out again through the parallel equivalent resistance.

@bain5872 10 лет назад

Another one out of the park. The theory reawakens the circuit nerd in me. I'm starting to design again. Good job!!! You covered the subject very well.

@macadamia1966 7 лет назад

Nice calculator! I bought a used HP 15C back in 1986 and I still have it and use it today, although I tend to use my HP 48GX more often. Great video and awesome examples as always. Thank you!

@1ManWrenching 10 лет назад

That square combined with sine output not only blew my mind, it was gorgeous looking. I had no idea that was possible!

@321reh 10 лет назад

Thank You For A Most Excellent Video Alan!!! Studied These Concepts In 1981 And I Must say I Forgot A Bit of This Theory....It's Amazing How This comes Back Once You Studied This Topic Before!!! Hopefully You'll Do More Of These Basics Videos!!! Thanks For All Your Effort On These Videos!!!

@Debraj1978 2 года назад

My one stop guide for opamps and analog circuit. Instead of hooking on breadboard to verify the calculations, I simply watch your videos. Though, I like the inverting configuration, but for most microcontroller related interfacing, the power supply is unipolar (and not +/-). Hence, I am forced to use the non-inverting, when I want to measure an AC input using microcontroller and hence need to give a DC offset to AC to make it compatible with the ADC input.

@w2aew 2 года назад

You can still use an inverting configuration for your signal and apply the dc offset to the noninverting input.

@Debraj1978 2 года назад

@@w2aew Thank you for the reply. Just to confirm, did you mean: - 1. Use an single supply opamp 2. Configure the opamp in inverting configuration. 3. Apply the AC signal to the inverting input 4. Apply the DC offset to the non-inverting input? In the above configuration, the AC signal source will not see the signal being applied to the GND, but it will see it being applied to another voltage source (equalt to DC offset)? Other than the easy calculation, is there any additional advantage versus non-inverting summing configuration?

@w2aew 2 года назад

@@Debraj1978 Yes, that is correct. You get no interaction between the AC source and the DC offset.

@JustSomeGuy1967 9 лет назад

Your videos are fantastic!!! I have always wanted to do electronics instead I became a paramedic until recently starting an ISP and have some time to learn and tinker. Between you, Dave and signal path I may one day invent something great (I will however settle for a good am transmitter)

@DAVET38 10 лет назад

Another interesting reminder of circuit theory. Thank you Alan.

@mengnan24 8 лет назад

Thanks. It helps a lot! Please bring us more circuitry tutorial videos at your convenience...

@AlexBlate 10 лет назад

I've been trying to get my head around "current-mode" op amps (as opposed to "voltage mode"). They seem interesting in that, in a typical configuration (according to a TI app note), bandwidth reduction is only a function of Rf, not the total gain. But I'm not clear on how an op amp can be sensitive to current on its inputs while maintaining a decent approximation of an ideal op amp (i.e., where zero current flows into/out of the inputs). Would you consider doing a video (or multiple videos :) ) on current-mode op amps? Cheers and thanks for all the great videos. I appreciate your clear and precise explanations of both the theoretical and practical/engineering concepts and applications. All the best from Chapel Hill, NC, Alex

@hdmalpas 10 лет назад

Very informative Alan yet again thank you.

@jcims 10 лет назад

Great video! Always helps to see the theory incarnate on a scope.

@startend7196 7 лет назад

Awesome lesson.

@stargirlgroup2009 5 лет назад

This is really helpful, thank you!

@DrenImeraj 10 лет назад

Could you do one on the op amp analog multiplier using the exponential characteristic of the diode. I always find that fascinating. Really good video, thanks.

@wendti 5 лет назад

Great explaination! Thank you!

@JonathanSterlingUSA Год назад

0:45...5:39 Thanks. I always wondered what circuit is required for combining 2 audio inputs. What does it look like with both waveforms at the same amplitude or both at the same frequency. The output waveform is not so pretty, I think. Now I know what keywords to look for, I can find all that stuff. Thanks.

@andymouse Год назад

Great tutorial....cheers

@jstro-hobbytech Год назад

Once again great video. For someone familiar with all the common amplifier circuits but wants to do a real world project using them to affirm what I've learned. What circuit would you reccomend for this one. The summing and peak detection amplifier circuit(s) intrigue me the most and I'd really like to wrap my head around the ways to make practical use of them. Once again. Add a thank you button haha

@JohnRaschedian 5 лет назад

Thank you for this video sir.

@StephenMendes 5 лет назад

The theory and calculations are in my video #9 in playlist "Basic Electronics for Beginners"

@jamesmasonic 7 лет назад

the best and neatest explanation on the topic. i appreciate these. just one thing. at the end of the video you mentioned about the inverting summer that one can invert the output by an inverting follower. but to do that one still needs a dual power supply right? how do you make dual supplies in your tests? i found some voltage converter ICs to obtain negative voltage. but I was wondering if you use such ICs and is it possible to use inverting summer circuit with a single supply.

@w2aew 7 лет назад

If you make your reference voltage (virtual ground) of the stages *not* equal to ground, then you can get away with a single supply - which is what I do almost all of the time. See my video on op amp power supply considerations.

@Garganzuul 8 лет назад

Could you do one about active ground plane isolation?

@phobehrphobehr5772 10 лет назад

Very good...thanks for posting..

@EdEditz 7 лет назад

This could be useful in a home build synthesizer to add signals from different oscillators. Very cool.

@lukitree 7 лет назад

That's why I'm watching this, xD

@EdEditz 7 лет назад

Haha very cool. I want to build one too. Got any good oscillator circuits?

@ottoomen5076 7 лет назад

Voltage Controlled Oscillator chips are available in all frequency ranges for less then 10$ if you don't want to build your own.

@Avionics1958 10 лет назад

great video, what will happen if you inject a Dc voltage to one of the inputs and at the same time inject AC to another on the summing side? will that raise the threshold?

@w2aew 10 лет назад

Yes - you can use a DC voltage on one input to add/subtract a DC shift in the output.

@DarrenLandrum 10 лет назад

Is this the basis of so-called "servo outputs" used in some audio circuits to avoid use of DC blocking caps? I've often wondered how that works.

@w2aew 10 лет назад

Most likely - I'm not familiar with this application, but it makes sense. There'd likely be some circuit that is servo-ing a DC bias on the audio path to line it up with the input needs of the next circuit.

@leppie 10 лет назад

Nice video! Is the result for the non-inverting case the same as an inverting plus invert stage's result?

@w2aew 10 лет назад

Not quite - I didn't design the gains to be the same. The "voltage divider" affect in the non-inverting case reduced the gain in that case.

@SJayanth 3 года назад

Thanks very much, sir.

@MrMac5150 10 лет назад

Top engineer.

@JurekPrzezdziecki 6 лет назад

Is summing op amp (non-inverting) the same as precision adder? I mean the amplification of the inputs should exactly 1.00 and is suitable to add control voltages for the pitch control of VCOs?

@w2aew 6 лет назад

You can design a summing amp with gain of 1 for each input, if that's what you'd like.

@JurekPrzezdziecki 6 лет назад

Yes, thanks.

@TechTins_Projects 10 лет назад

The isolation of the input voltages looks and feels so very right. Why not always use an inverting opamp with a follower? Presumably using the noninverting would save a little power? (ie. save using an extra opamp follower). But could there be other benefits in some other situations?? Would using a non-inverting OpAmp for summing voltages be an unusual case. Just seems redundant somehow. This is fascinating. Top video again!!

@w2aew 10 лет назад

I agree - the inverting summer's advantages are really nice, and will often be worth the "cost" of an additional inverting follower. Or, sometimes the inverting summing amp is all you need. The tradeoffs and requirements dictated by the design (power, functionality, cost, available supplies, etc.) are too varied to make a general recommendation of course.

@TechTins_Projects 10 лет назад

Thanks Alan. That makes total sense. I'd never considered that the direct connections to virtual ground with the inverting summer had such a neat advantage. Really nice to learn about that. Another little golden nugget of info! "tradeoffs and requirements dictated by the design (power, functionality, cost, available supplies, etc.) are too varied to make a general recommendation of course" I think these endless design choices, in an odd way, also add to the fascination! Keep the lectures coming they are superb. Amongst the very best on youtube.

@billwilliams6338 4 года назад

What causes a DC voltage measured on the amplifiers speakers jacks that is caused by the output amplifier circuit? If you're measuring a DC voltage on the amplifiers speaker jacks what would cause a DC voltage to be measured on the speakers jacks of an amplifier?

@w2aew 4 года назад

Depends entirely on the design of the amplifier.

@RAndrewNeal 4 года назад

So why are R1 and R2 not the same value? A few of the things you mentioned were a bit over my head, currently; such as superposistion. Are you adding them together in a fashion such as 1*1 + 1*0.5?

@w2aew 4 года назад

They can be the same value, I was just pointing out that they *could* be different if you needed to have more gain applied to one or more of the signals being summed together.

@RAndrewNeal 4 года назад

*+w2aew* Oh okay cool, I must have missed that part.

@NNNILabs 6 лет назад

What if we add diodes to the inputs of the non-inverting summer? That should prevent any interaction.

@w2aew 6 лет назад

That wouldn't work. Instead of being a summing amplifier, it will wind up being a "highest input voltage wins" amplifier.

@NNNILabs 6 лет назад

Aah right, I remember seeing a design like that somewhere.

@quantomic1106 10 лет назад

Yet another comprehensive video from Allan. You really know your shit!! : ) By the way, is it possible for you to make a video on current sources? Also I would like to know how to convert square wave to sine wave if possible. Thanks and keep up the awesome work!!!

@w2aew 10 лет назад

Yes, current sources are on my list....

@quantomic1106 10 лет назад

***** Great! Thanks!

@bmbutt30 9 лет назад

Hi, i want to make a binary weighted DAC with op amp LM358 or any. by using only one power supply, not dual supply. so how i can use inverting configuration for the binary weighted Summer or DAC? i want to make 3 bit DAC. any Idea? i am simulating but at some point i do not know what is wrong happening.

@w2aew 9 лет назад

If you're using an inverting configuration, then the response of the DAC will be inverted. However, this is easily fixed by following the summer with another inverting stage. The LM358 is not a good choice for single supply operation of this function because it is not a rail-rail op amp. You should replace it with a rail-to-rail op amp. Make it a dual op amp, and you can accomplish the DAC and inversion with one chip + resistors.

@bmbutt30 9 лет назад

***** hi again, thanks for the reply. can you suggest parts numbers to be considered like op amp for single supply. i do not get one point " this is easily fixed by following the summer with another inverting stage " you mean output of this amplifier must go through inverted buffer with gain of 1? please suggest some parts. thanks in advance.

@w2aew 9 лет назад

Bilal Masood I'm sorry, but there are literally hundreds of possibilities. The design constraints in your application (power supplies, logic levels, power consumption, etc., etc.) can help to pare these down. At the end of the day, there will still be MANY devices that can likely be used. Yes, when I refer to a second inverting amp, it can be a gain of -1, or even something more - it all depends on how you scale the the first stage.

@BR. 8 лет назад

Very good tutorial! Which OpAmp would you recommend for a battery powered audio mixer? Ideally, I was thinking of using one LiPo cell so I suppose it should work all the way down to 3V. Also, I was thinking to base the mixer on a circuit similar to this one: www.all-electric.com/schematic/simp_mix.gif (circuit 4)

@w2aew 8 лет назад

All of those mixer circuits assume a split supply on the op amp (you can tell this because the use a ground reference). The "go to" op amp for these applications is usually the NE5532, but it won't work on such a low supply voltage. Here's a good "selection page" for low power, low noise op amps that would be suitable for an audio mixer application: www.ti.com/lsds/ti/audio-ic/audio-operational-amplifier-product.page#p1typ=0.7;3

@vtgordo 6 лет назад

Why is the input 'opened' for superposition for the inverting case, and 'shorted' for the non-inverting case? I can see that it works physically, but that seems arbitrary

@w2aew 6 лет назад

For the superposition calculation, the input voltages not being computed are shorted - in both cases. Did I mis-speak in the video somewhere in the video?

@vtgordo 6 лет назад

Nope - my mistake. About 1:20, I thought you said that we opened voltage sources and shorted current sources, but you said the opposite. That was my confusion. After re-listening, it became even more clear. Love the series! I wish I had you and EEVblog (and the internet in general) many years ago.

@47Lancelot 9 лет назад

can you call this "modulation" ?

@w2aew 9 лет назад

Not really. It is called summation. Modulation involves changing the amplitude, frequency or phase of a signal - which involves more than simply adding two or more signals together.

@jstro-hobbytech Год назад

I've never seen a curved square wave.