That's a really interesting little circuit. I will certainly keep it in mind if I ever need to incorporate a window comparator in a future project. Thanks for sharing.
Wow, the way you explained this was amazing. This is probably the first time I fully understand the concept of window comparators lol. Great job. Thanks!
Wow. Thank you for giving your video to the internet at large for the rest of us to learn from. I really like the way you've changed the visual by updating the values to show the effect of different inputs. Jim WIlliams would be proud.
Seriously, I have found some of the absolute best circuit designs or gotten the most 'ah ha!' moments from older books anywhere from Forrest Mims Radio Shack mini notebooks to stuff like you're showing at the intro! There is always so much to learn in the world and I can't learn enough, fast enough and it drives me crazy 😊 -- anyone else relate to any of the aforementioned? Take care! 😊
You could slide both low and high thresholds to positive (or negative) by just sliding the non-inverting input of the op-amp with a voltage divider (a trimpot).
Awesome little circuit. One of your other vids already inspired me to order that book. It looks to be full of goodies. You do a nice job explaining things. Thanks for sharing.
Thanks for the wonderful video clip. Your treatment is quite comprehensive, especially considering you mentioned, at the end, some shortcomings of the circuit. I guess Hysteresis is another one...
I'd only add that this circuit falls apart under high speed operations, for two reasons. 1. The opamp is being driven into saturation, and it takes time for it to drop from the rail down to 0 volts. 2. Diodes have a capacitance associated with them, which forms a low-pass filter in conjunction with Rin.
Nice circuit indeed. I think the better explanation of the 0.65 V output in the first example would be better started as "the inverting input is held at 0V by the virtual short between the opamp (with feedback path) inputs, and the fact the non inverting input is tied to ground.". It's not set by the diode forward voltage drop, the opamp output is, though.
Thanks for the great explanation and clever circuit. You sold me on the idea of looking for some old databooks and reference notes. I've been playing around with the cheap little $2 Chinese dual volt/current meter circuit lately. They only used 1/2 of the LM358 for their current sense amp on the device. That got me looking into ways of creating a crude auto-ranging design using the other 1/2 of the op amp. I never imagined there was a way of using one op amp for a 3 way comparator (mind blown). I don't want to build a dual polarity supply for a circuit like a simple low resolution meter but it's definitely a little circuit I want to try out. As a simple hobbyist myself, I have had a hard time finding examples of simple and easy to understand switching networks that work. I haven't gone through all of your uploads yet (but will shortly). The two places I've struggled with when it comes to switching networks are how to vary the gain to a meter while maintaining linearity, and how to build a switching network for an adjustable linear power supply somewhere between multiple secondary windings of a transformer and the regulator IC. Both are rather simple design elements. I feel like I'm beginning to understand circuit design well enough to figure these out on my own but I could really use a working example instead of learning to design through the magic smoke of failures. I don't expect you to do anything I ask or request or anything like that. I'm not trying to tell you what to create content about. I'm simply trying to relate an area of interest that seems lacking in visual instruction on this platform. Again, I'm just a simple hobbyist. I got into electronics a few years ago after becoming partially disabled. This account is not monotized, nor do I plan on it becoming so. I'm just here to learn and share a thing or two if I come across something interesting. I added this video to my op amp notes playlist and I'm sure I will add many more of your videos to my list of things to goof around with. Thanks again for taking the time to share and explain this circuit to strangers like me. -Jake
Wow what a neat circuit and wow a great video you have made! I am a noob but could follow every step all the way, thanks to your step by step understanding method. Maybe a little question, could you not make the comparator more precise by using variable resistors instead of standard value resistors?
How about using a voltage divider (2 resistors) on the non-inverting input? I haven't done the math, but my 'Mark-1' brain tells me that this might obviate the need of the summing network?
The question to test a designer's IQ would be this: if you had no other source other than the battery to be tested for voltage levels, how would you design that circuit for battery level indication?
+Zinahe Asnake Any of Jim Williams’ books and/or app notes are excellent reading! "The Art of Electronics" is of course an all-around classic, and a great reference to have around. Jerald Graeme has written several books on op amps (including this one), all of which I liked, and there’s always Walter Jung’s "IC Op-Amp Cookbook" too. For filter design, I really like "RF Circuit Design" by Chris Bowick and "Electronic Filter Design Handbook" by Arthur Williams. If you’re looking to learn about oscillator circuits, IMHO "Crystal Oscillator Circuits" by Robert Matthys is probably the best intro book on the subject. One of my favorite books though is "Modern Electronic Circuits Reference Manual" by John Markus. It’s one of those books that was relevant before you could find everything on the internet (I have the one from 1980), but it has thousands of circuits, each nicely categorized into specific sections, and tells you what book/magazine each circuit came from (which can help lead you to other books on a specific subject of interest). It’s especially useful when you might not know exactly what to Google for, or for just perusing (“Hey, that’s a really useful circuit, I’ll have to keep that in mind for my next project!”).
So... the equations for E1 and E2 in the book are wrong, the equation for E1 should be for E2 and vice-versa. Also they are missing a (-) sign in front of the R1/R2 term. Right ?
I think I see what the author has done. If you take V_ and V₊ to be equal in magnitude (absolute values), but opposite in signs i.e. V_ is negative and V₊ is positive, then the equations for Vtl (E2) and Vth (E1) are correct. But if you take them to be with different magnitudes from one another, then the equations don't add up because Vtl (E2) is tied analytically with V₊ and Vth (E1) with V_
+n3tpr0b3 Yes, I see what you're saying; the equations in the book are also somewhat ambiguous in that there are two resistors labelled R2. If both R2 resistors are equal value, and if V+ and V- are of equal magnitude, the equations in the book work as-is. If, however, you use the book's equations with the absolute value of ER (the offset voltage), then they will work regardless of the magnitude of V+ and V- or the values of the two R2 resistors, provided you then take the absolute values of the resulting E1 and E2 voltages. Note that in doing so, E1 then becomes the low trip voltage, and E2 is the high trip voltage.
+devttys0 Yeah, that will work too, but then the graph provided will not make sense. I think that the author should have been a bit more specific about it :-)
