Thanks for these videos. I'm now a retired hobbyist and I've been modelling these circuits in a simulator as well as wiring them up on breadboards. I remember that as an impatient and impulsive undergraduate decades ago, although I was very keen to learn, I never could get my head around op-amps and I eventually flunked out out of electronics to do something else. In those days, of course, there was no internet and no circuit simulators. I do regret the wasted opportunity to learn something that could have given me a completely different career.
Honestly, thanks for the quick show & tell regarding the Dual Power Supply. Being a retired theorectical mathematician & only an occasional electronics hobbyist that wants to build a instrument pickup pre-amp for the stringed instruments I build until you had demonstrated the structure of Dual Power I had assumed in my experimentation that the typical battery circuit of +/- was being depicted in diagrams regarding the lm741. Thus I had not been able to get the Lm741 I was experimenting with to act in the non-inverting scheme at all. Once I saw what you were doing I quickly made two 6 volt battery packs and turned them into a Dual Supply of (6+, Virtual ground, 6-). I then reconnected the lm741 under both schemes and wala I had both a non-inverting then inverting amplifier. The interesting thing is that often many things are left out in explanations that depending on the audience need to be included a bit like anyone's first lesson in computer coding where it's drilled in to the student that what has meaning to you is not sufficient if the computer is to output the aim.
Excellent video, expanding my understanding nicely. A little more technical than some of the other basic op-amp videos I've watched but one can't stay in the shallow end of the pool forever.. :)
To separate the portion of rise time that results from high gain on a tiny portion of the sine wave, from actual slew rate, throw a square wave on the non-inverting input and measure the rise time on the oscilloscope. That's your slew rate. High gain on a sine wave might not be hitting the slewing limit of the op-amp.
It seems you use a solderable BNC connector to "break" out the signals from the sig gen to the breadboard. You can see the center lead of the BNC connector going the breadboard, but the shield/GND lead is not clearly visible. It seems to go to GND, but it's not clear if it is 50 ohm terminated or not. Can you give a clearer picture?
I made a buffered phase shift oscillator with Lm324 . Gain of 8.333 . I used all op amp of the quad but I’m having issues identifying where to connect the non inverting pin 3 of the IC
See the link to join the community in the description. Great place to connect with other engineers and makers. Very friendly and knowledgeable group. Welcome!
Very nice video. What missing for me - doesn't explain 2 things: 1. Comparator oscilator where is use possitive and negative feedback 2. Trick's where on the feedback is use resistor plus cappacitor. They are in parallel between self and even I dont understand what for. Simply moar pls about a bit advanced opamps circuits :)
Hi wegi. These are definitely subjects for a more advanced video. I haven't considered comparator/relaxation oscillators, so that would be a topic that could be interesting. It is there to prevent oscillation (due to bandwidth limiting). You'll see this in the next video - I don't go through the calculation (some things I can't drill down too far into on a particular topic), but I used it to help limit the audible noise. -Derek
I have a question regarding the LM741 is it suitable for signal amplification from 50 microvolts like 50 times and why its not used much in biological signal amplifiers. And why using the much expensive instrumentation amplifiers?
@@profrook Kit G is right on target - offset voltage and current. The LM741 may be ok for general purpose stuff, but there are many other op-amps that are MUCH better suited for precision tasks in the microvolt range. It's worth going through different vendor parametric searches to familiarize yourself with performance characteristics. I chose the LM741 because it's well known... I don't think I pointed out that it's a really old design and not that great of a performer. I think I note this in the upcoming video. -Derek
Fixing the offset is easy so that's not really a reason. 1. Stability is more likely the reason; it must remain perfectly differential over a wide range of possible inputs and temperature variations. 2. Absolute input levels matter! The *difference* of inputs might be only a few microvolts, but common mode noise may be several volts over-driving the input transistors (or FETs or whatever). In a typical biological environment is likely to be all sorts of electromagnetic emitters radiating interference. 3. Safety: The inputs must be isolated! No voltage or current can leak back into the probes. If there's any feedback connection from output to input, and there usually will be, that feedback is also going to reach the probes and could induce unwanted biological activity. So basically you need something like emitter followers on both inputs so that the point of insertion of the feedback is NOT backwards to the probes. Doing so will alter the feedback strength and thus the gain would fluctuate unpredictably.
I wonder if anyone can shed some light on my question. In 1974, as a trainee, I was taught by an old retired instructor that Op Amps were called that because they were the practical result of designers trying to design the perfect amplifier. Such an amp would have infinite input impedance, zero output impedance, infinite gain, etc. So it was named an "Operational" amplifier as opposed to a theoretically "ideal" amplifier. However, I have seen on another youtube channel that they were so named because they can do mathematical operations. Does anyone know the correct reason for the name of Operational Amplifier? No guesses please, and if possible can you quote your source. Thanking everyone in advance for your input (non-inverting).
I dug out an old Air Force technical training manual dating from the mid 1970's and the chapter on operational amplifiers begins with the following:- "The term "operational" refers to its original use in performing mathematical functions". It then goes on to describe the ideal amplifier for mathematical functions (as you did above) and concludes that although the ideal amplifier is unattainable, the current designs are a close enough approximation. Analog computers of the time made extensive use of op amps so I've always taken 'operational' to mean 'mathematical', rather than 'practical'.
@robert noonan the other reply from @steve murray is correct. And the proof is this line im quoting from the chapter 'operational amplifiers' from the book 'handbook for design and applications' by Tietze and Schenk: `…Amplifiers of this kind were at one time used exclusively in analog computers and for performing mathematical operations such as addition and integration - hence the term “operational amplifier.” `
I really enjoyed this. Doing the four comparisons together and stepping through them was very clear and concise. It's definitely helped me understand the subject better. Thank you.
Easy to digest explanation. Thank you! 🙂 I really like that you split more example circuits into another video and kept this to a bare minimum of 4 basic op-amp configurations 👌
Thanks for the explanation, but I caught a couple of errors in the diff amp and current sources: The diffamp you drew should be using PNP input BJTs for the INV and NON-INV inputs and your inputs are in reverse. The current sources should have 2 diodes at the base, because Iout = Vb-Vbe/Re = Ve/Re. In your schematic Ve=0, because Vb is completely consumed by Vbe because Ve=Vb-Vbe and Vbe=Vf of the diode. At the beginning of the video you mentioned circuits we would like to see. I've been looking for an accurate voltage gain stage for a low voltage (low mV range) DC signal, that can be implemented with BJTs. With just the diffamp, I've only ben able to get a voltage gain of 5Vi, if I attempt anything above that, the signal hits a ceiling of about 1.4V and I'm trying to keep the component count to a minimum.
Hey Derek, still my favorite Tattooed electrical engineer! If I added a Schmitt trigger to the output of the comparator, That would in fact solve the issue of the slue rate correct? By ALMOST creating a much cleaner square wave. I think. Just the new guy here!! Thanks again for all the great training you and your crew provide!
I have a whole box of Op Amp, the problem usualy is that when I build a project I don't have the specific Op Amp I need. I would be very interesting to know how to fin an equivalent or substitue for an Op Amp
Sir I'm taking the liberty to request you to please make a detail video on Remote Control circuit's used in the RC toys cars etc , how they work ,what is the function of every components used to build the RC circuit , how the signal is transmitted from transmitter to receiver to control the motors used in the toy Please do it Thanks
comparators usually have an open collector on the output so a resistor must be used to limit the current sinking into the IC. I'm using an opamp with a pnp BJT to build a linear voltage regulator. LM324 or LM358 have an output current limit in the datasheet. Does this mean that I have to use a resistor on the output of an opamp when driving a BJT?
Hi Farhad. Yes, it is always a good idea to stay within the bounds of the op amp source and sink current. I don't know exactly what you have attached to the output of the amp, but I'd calculate the impedance looking into the BJT and see if the base current is within bounds.. for the '358, that's 40mA source. -Derek
The limitation of an open collector circuit is if it drives a capacitive load. The transistor can charge the capacitor rapidly but only the resistor can discharge it per the r-c time constant. That's why the totem-pole arrangement of the op-amp output is much better if you are driving a capacitive load.
hey man. I'm looking to boost a 4 volt signal for a door bell that goes to an old celestion 12 inch amp from the 70s. there's no power outlet near it is why I ask and the button to speaker distance is about 50 meters. I was thinking an opamp to buffer circuit that boosts the 4 volt signal to about 10. which ic should I use. the amp looks like the day it was bought 40 years ago with perfect tweed covering. haha the makerspace is in an old catholic girls school and the inherited the old guitar amp. well it's not a proper amp as it only has a mono jack input hence my question. it only needs to be about 50 percent louder. thanks brother.
how about the Vishay IL300 linear optocoupler as a plus and minus 0 to 10 vdc in and out. most of the videos seem to just go for positive 0 to 10 vdc not both. 🧐great video, thanks a lot. i think it would be interesting to use the 741 op-amp or something like it for long term parts in the future.
Are there fundamental substrate-level tradeoffs between slew rate/bandwidth and noise? I've noticed that jellybean op amps tend to be spec'ed for either one or the other, but not both.
Great video. Where can I learn how to properly choose the resistance values? (Since there are several options, including the option of using potentiometers)
It can be confusing to choose those values but for opamps, they are fairly easier. And it depends on which resistor you are talking about, depends on what configuration you are using. You will usually assume the value of any one of those resistances, just some made up numbers, and then the other resistances will be derived automatically. it also depends on the output, theres a lot of factors that the resistance vlaues depend on.
Thanks especially for the hands-on part. It is easy to get overwhelmed with the theory and reading about ideal characteristics, but it is completely a different feel to see things in actual work. Also liked the internal op-amp diagram and condensing them to a more digestible diagram. Excellent quality and great effort put into this. Thanks a lot.
