I love that you use the 741 here. This clears up a lot of questions about dual supply requirements for the 741 (and others)! Thanks for moving slowly and deliberately for us beginners. I also learned a few new things about viewing signals on Oscopes in this tutorial. Thanks for making this!
I have been watching various opamp videos over the last week or 2. this is by far the best demonstration and delivery of Info on this subject I've found yet. You answered many questions I still had with both on paper and physical examples. Lemme see what else you've posted!
This is an 'old' video. But a very important one! Many people, including yours truly, blindly use an op-amp and then wondering why it is damaged or why sellers con us, we then buy some more and same story, we buy even more and same story. Lots of wondering and blaming.
@@stevegoodjob5902 To put it simply, many people using an operational amplifier or transistor without understanding how it works. This is what I mean and is the problem. Problem is the human and not the operational amplifier or transistor. For instance, many people wonder why audio or signal clips or looks weird. The first thing they do is keep changing and buying different op-amp or transistor to test. They do that until a period of time they get fed up and start to blame the maker of op-amp or transistor. How is it possible that all transistors of all makers fail all together with 99.999999% rate of coincidence?!?!??!?!?! For some weird reasons they are not bothered to change other components and try different levels of power/voltage/current. They are somehow braindead. Doing the same thing expecting different results. You would be surprised the sheer amount of people having an oscilloscope still wonder why a circuit does not work as expected, and play the blame game. Any fools can own an oscilloscope these days anyway. As if having a digital clock and wondering how come it does not have the good old hands moving, that clock must be faulty, buy another digital clock and wonder why again no moving hand, must be another defective clock, buy some more, wonder some more, rinse and repeat.
I've been watching your videos for years, and it just hit me that your notes are actually analog Power Points!!! Thanks for all the theory. Very useful stuff!!
Man, having the horizontal lines there makes this crystal clear for me. Always been kind of fuzzy when playing with this on my own scope. I’ll have to make sure to draw those in. Nice trick 👍
Thanks Alan - like many others I refer back to your tutorials often. You balance theory and practical perfectly every time. One thing to note here is that rail-to-rail op amps are expensive! Order of magnitude up on the likes of an LM358.
BTW. Do not go too much beyond power supply range with your input. The AD8032 does support going about 200mV below (above) negative (positive) supply safely, and still maintain linearity of output vs input (obviously you would use gain less than 1 in this case usually). Above that the linearity (and distortion characteristics) can't be guaranteed. Additionally, 500mV is stated as a absolute maximum, beyond which opamp can be permanently be damaged. It is recommended to add external clamping diodes if you expect this to be possibly happening.
I have to thank you for your efforts to explain many interesting things in electronics. I have weak knowledge in this field. This video help me better understand about op amps things.
2nd time watching in as many days. Great videos! Having graduated in '88 with a BEET degree. I decided to try out these new fangled single supply op amps i.e LM358 lol.... After some frustration and thinking they somehow magically used a single supply your video set me straight. Doh!
#2 view. Great work W2AEW. This is better instruction than at our local community college. My neighbor is taking electronics classes there and I shared your videos with him. He is impressed.
This did answer some questions! Questions that I didn't think of asking! Do you _teach_ the subject? Because you seem to know possible questions students will ask. Thank you very much for this video!
Great delivery and information. I appreciate your ability to share the knowledge you have in a logical, easy to understand manner. Keep up the great work. By the way, I decided to subscribe. Thank you.
12:50 "And you plug it in, ... boom ..." Boom??? Reallly??? :-) But in general, there is a (small) perturbation near their zero, though. Good, very good, video. Second point, if the op amp has its offset not defined as being the earth ground we have to adjust the + and - signal with respect to the same zero origine... which can then be THE real headhake. I really hope everything is fine on your side, it is 2021 here!
older amplifiers used transformer less power transformers, it was called hot chassis which didn't use an AC power transformer but a series of tube filaments to step down the AC voltage. I'm not sure how tube filaments step down an AC voltage, but many you might know. On the schematics it looks like 4 to 6 filaments stepping down 120VAC to 40VAC for the rectifier tube.
As always, a great video Alan- perhaps in a future installment you may touch on the areas of device types (e.g. bipolar vs MOSFET) and how that affects ability to drive near the rails, slew rate (speed) considerations (e.g. why use a bipolar op-amp vs MOSFET for speed), etc. Great little tutorial with very nice demonstrations. 73 Bill N4BKT
Thank you so much or this excellent video which clear out some confusion on the rail to rail and split supplies concepts. I can't wait to see more OP-AMP tutorials (if you have more coming).
The schematic on the last page of my notes is accurate. In my case, the signal generator features a floating output (the shell of the BNC isn't grounded), so I was able to put it in series with the supply that I used to adjust the offset.
Well, from my interpretation, what you're calling a "virtual ground" is just a voltage reference. You could also call it an "ac ground" because of the very small shunt impedance due to the capacitor. The actual virtual ground exists on the "-" input, not the "+".
Thanks for the great information. I was, however, hoping to learn a bit about how to calculate the power consumption of the op-amp. So.. if the output feeds say an ADC, how do we calculate the power loss through the gain resistors and the chip itself. Once again, great tutorial. Thanks.
Well done! What is the most effective method to bias the op amp using single power supply? Would it be split resistive or using other means? Thank you for your great to the point presentation!
At around the 2 minute mark, I don't think that point should be called virtual ground, unless it's a term that is used pretty loosely. Virtual ground for the op-amp would be there when you have the positive terminal connected to GND and negative feedback configuration, where the feedback action is trying to make the voltage at the negative op-amp input equal to the voltage at the positive input. In the circuit shown at the 2 minute mark, it looks like an open loop.
If my question was answered 9 years after the video was published the question would be out of what is indicated below: Suppose your using a little module using a lm358 IC that was purchased out of China and pre-assembled to serve as a Mic or transducer preamp as I expect to use mine. Suppose the module has four pins with one for input from a signal source, one for output of signal from the lm358 and two pins for power supply. Suppose you do as I did which is connect two 4 pack AA battery packs in series and supply power to the module with the free end of the one battery pack leading to Vcc and the other free end of the battery pack leading to what one might call Vee on the lm358. The question then is what would you use as ground or the 0 volt reference point for the input and output signal? I have used the Virtual Ground created by where the two battery packs are physically connected thus I suppose the signal swings between +6 volts and -6 volts & I have used what leads to what I have called Vee serve as the ground for the signal's input and output and see no difference on my scope under each scheme. Any comments on this, to me, puzzle would be greatly appreciated.
Assuming you module was designed to be a mic preamp, then the input is most certainly AC coupled, so the ground reference for the signal doesn't really matter - it could be either supply rail or the virtual ground because from an AC standpoint, they're all the same (all shorted together with capacitors.
it's very informative..can you upload more videos about other useful op amp applications, like half/full wave rectifiers, differentiator/integrator, window comparator and etc.. tnx
Super useful. Are there some performance tradeoffs to the rail-to-rail opams? Noise, bandwidth, input voltage offset, temperature stability, drive/sink output current, etc.
yes true, I just didn't know that different tube filaments has different resistance values which is a voltage drop. I thought as tube filaments all had the same resistance value.
But electronic engineers and technicians say that the laminations changes the frequency response of the transformer is this true or false? or do they mean the core material inductance will change value because of the wire winding lamination?
What are the advantages of using Two Diode Full wave rectification compared to using 4 diode bridge full wave rectification? The Two Diode Full wave rectification has benefits how so
Great video, very easy to understand, I am building an audio signal generator and you can use eiher 6 volt sprit or 12 volt single, can you tell me which way to go? Thank you kindly!!
From a circuit performance standpoint, they'll be identical. So, it really comes down to details of your requirements. Do you want the output to be centered around ground and DC coupled? If so, then use a split supply.
Around 1:50 you mention you AC couple the bias to ground "to keep it stable" can you point me in the direction of where I can get some additional information on that? I'm going to guess you mean the capacitor will keep the voltage "less spikey" and closer to a flat line? If that is the case I'd think you'd have to carefully select the cap so it let low frequencies pass but not high ones?
Hi, we can make an offset on the positive input simply using a resistor divider, but how can we offset the negative input which takes the input signal without using an additional power supply? thanks
What is the purpose of the 2.2k resistor at 7:30? I’ve seen these before, or even in the feedback loop of unity gain buffers, but never understood what they’re for?
In old tube amplifiers the 6vac heat voltage the transformer didn't have a center tap for the ground for the 6vac. To convert a non center tap transformer to a 6vac center tap you put two 100 ohm balanced resistors and tie them to a virtual ground which will be the tubes plate voltage. Most plate voltage are from 200vdc to 450vdc. Not sure why they would put the virtual ground to a DC potential connected to the plate voltage so that the 6vac heat voltage will have a virtual ground virtual center tap. Have you heard of this type of virtual ground?
What formula can you use to convert Full wave AC voltage to the Equivalent Half Wave AC voltage and vise versa? Because if a circuit needs 26vac Half wave voltage, how can you convert this to the equivalent Full wave AC voltage?
My question is that you used a variable voltage source to make an offset on both the positive and negative inputs (schematic 7:55), thus your input signal that you want to amplify is floating relative to ground, what if the input signal is not floating? how can i make an offset on the input signal, can i use a voltage divider, what if the input signal source has a very large impedance, should i use a buffer before? thanks
Can you make a video lesson about measuring power supply rejection ratio and also power supply control loop stability? They make special probes called power rail voltage probe, which i have never used one and don't know how its so much different
I'll add that topic to my list. Power Rail probes are special, wide-bandwidth, low-attenuation probes that allow you to dial-out the supply rail voltage, and concentrate the high sensitivity measurement (maybe 1-2mV/div) around the supply rail (large DC offset).
@@w2aew Back in the 60's and before they used "bootleg grounding schemes" because it was just a 2 prong Floating Earth and not using a 3 prong with an earth ground. When a piece of equipment is wired as "bootleg grounding using a 3 prong cable" ( Not 2 prong ) the DVM meter will be connected to earth ground or circuit ground. When making In-circuit voltage measurements all the voltage measurements are going to be incorrect and wrong because the equipment is wired as bootleg grounding? because when you disconnect the earth ground wire/bootleg ground the in-circuit voltage measurements on the DVM meter are going to be correctly different, any reasons why?
Hi, very instructive video. What is the role of the 2.2k resistor connected to the + input ? The one that has its value in parenthesis, it is seen in the drawing of your example circuit at around 8:00 . Sorry if that question was asked already.
A resistor is usually used in that location to help minimize offset due to the input bias current of the op amp inputs. The value is usually equal to the parallel combination of the resistors connected to the inverting input, so it *should* be approx 1.4kohms. I used 2.2k simply because it wasn't critical for the video topic, and it was laying around on the bench near the breadboard ;-)
Thanks for the explanation! As far as I understand, since the gain here was less than 1.5, I suppose even this resistor wasn't necessary because the error would have been very small. Nevertheless it is important to know about this stuff. I was able to find a bit more in-depth about this watching EEVblog #479.
for a balanced signal input, where you have a floating differential signal going into the +/- terminals of the opamp, a split supply would be more necessary correct?
Great video. thank you very much. What happened to output swing voltage if the output current is increased? how to use opamp to drive a low impedance load?
It depends on the specific op amp. In general, the available voltage swing is reduced into low impedance loads. Some op amps can drive low impedance loads better than others. Often times a buffer designed for low-impedance loads (like a push-pull stage) is included in the feedback loop of an op amp to improve the low-impedance drive capability.
@@w2aew Acutally I used push pull or single transistor at the output stage of opamp; it works fine but not efficient. With single supply, the output voltage has the dc offset.
I have a 741 op amp with a 170mV, 852Hz input sine wave, +5/-5V power. I have a 10k resistor from the inverting terminal to ground and a 20k feedback resistor (output to inverting terminal), the input is on the non-inverting terminal ... the gain should be 3... but instead the gain is roughly 1. (So the output is roughly 170mV.) The output is not clipping... I'm not sure what's going on...?
if your opamp circuit with a virtual ground connects to a another opamp that is using a single supply (ex 0-12V), in the gain loop of a non-inverting amplifier, would you connect the resistor to the 0V ground of to the virtual ground?
I have tried measuring the AC line noise on the primary side of various equipment on an oscilloscope but not sure how do it correctly. How can you measure the AC line noise level using an oscilloscope or is it better to use a spectrum analyzer to measure AC line noise? my Fluke DMM meter can't measure the AC line noise level so what meter would do this?
I love that you use the 741 here. This clears up a lot of questions about dual supply requirements for the 741 (and others)! Thanks for moving slowly and deliberately for us beginners. I also learned a few new things about viewing signals on Oscopes in this tutorial. Thanks for making this!
Still useful information in year 2019. That's 6 years after publishing! Some things don't change.
I have been watching various opamp videos over the last week or 2. this is by far the best demonstration and delivery of Info on this subject I've found yet. You answered many questions I still had with both on paper and physical examples. Lemme see what else you've posted!
This is an 'old' video. But a very important one!
Many people, including yours truly, blindly use an op-amp and then wondering why it is damaged or why sellers con us, we then buy some more and same story, we buy even more and same story. Lots of wondering and blaming.
What do you mean? Where is the problem?
@@stevegoodjob5902 To put it simply, many people using an operational amplifier or transistor without understanding how it works. This is what I mean and is the problem.
Problem is the human and not the operational amplifier or transistor.
For instance, many people wonder why audio or signal clips or looks weird. The first thing they do is keep changing and buying different op-amp or transistor to test. They do that until a period of time they get fed up and start to blame the maker of op-amp or transistor. How is it possible that all transistors of all makers fail all together with 99.999999% rate of coincidence?!?!??!?!?!
For some weird reasons they are not bothered to change other components and try different levels of power/voltage/current. They are somehow braindead. Doing the same thing expecting different results.
You would be surprised the sheer amount of people having an oscilloscope still wonder why a circuit does not work as expected, and play the blame game. Any fools can own an oscilloscope these days anyway. As if having a digital clock and wondering how come it does not have the good old hands moving, that clock must be faulty, buy another digital clock and wonder why again no moving hand, must be another defective clock, buy some more, wonder some more, rinse and repeat.
Thank you! Finally someone who can explain the difference for connecting split and single power supplies to beginners.
binge watching all the circuit tutorials, trying to remember to like and comment on each as well
Oscilloscopes are so cool! I just got a cheap one, but it is so fun to play with!
Wow, this could have save me a lot of pain back when I was figuring out the limits of a 741 the hard way.
Very well explaind. Doing and showing works better then text books.
Flawless presentation and demonstration of material. Thank you.
Really great tutorial. Clear and simple diagrams with a delivery style that I found very easy to follow.
Thanks to you I finally understood why my 741 is behaving in such a weird way, liked and subscribed
This is much better than using a powerpoint :D
Just a man, his pen, and some graphing paper.
2022 watcher. thanks for this! helps a lot when u dont have split supply
I've been watching your videos for years, and it just hit me that your notes are actually analog Power Points!!! Thanks for all the theory. Very useful stuff!!
I really like the way you explain. You always go the right level of the viewers. Thank you very much for all your effort and time. Good bless you
Man, best teacher on youtube
Man, having the horizontal lines there makes this crystal clear for me. Always been kind of fuzzy when playing with this on my own scope. I’ll have to make sure to draw those in. Nice trick 👍
Thanks Alan - like many others I refer back to your tutorials often. You balance theory and practical perfectly every time.
One thing to note here is that rail-to-rail op amps are expensive! Order of magnitude up on the likes of an LM358.
Keep looking. There are many inexpensive rail-rail op amps out there. The Microchip MCP6001 can be found for less than $0.25
@@w2aew Cheers Alan! Thanks for the heads-up.
BTW. Do not go too much beyond power supply range with your input. The AD8032 does support going about 200mV below (above) negative (positive) supply safely, and still maintain linearity of output vs input (obviously you would use gain less than 1 in this case usually). Above that the linearity (and distortion characteristics) can't be guaranteed. Additionally, 500mV is stated as a absolute maximum, beyond which opamp can be permanently be damaged. It is recommended to add external clamping diodes if you expect this to be possibly happening.
Your videos are really instructive.
I decide to watch 2 vids of yours every day from now on.
Great information! I very much appreciate when you show the "visual" of what is actually happening within the circuit! Thank You!
Thanks for sharing! I review this video each time I use an op amp to refresh my memory.
I have to thank you for your efforts to explain many interesting things in electronics. I have weak knowledge in this field. This video help me better understand about op amps things.
2nd time watching in as many days. Great videos! Having graduated in '88 with a BEET degree. I decided to try out these new fangled single supply op amps i.e LM358 lol.... After some frustration and thinking they somehow magically used a single supply your video set me straight. Doh!
#2 view. Great work W2AEW. This is better instruction than at our local community college. My neighbor is taking electronics classes there and I shared your videos with him. He is impressed.
as always your tutorials are great...why in schools we dont have teachers like you?
Extremely effective explanation! Thanks!
Thanks, seeing the behavior on the scope helped solidify my intuitive knowledge.
Excellent video. It's great opamp demo of single supply rail to rail operation.
beautifully described and explained thank you
This did answer some questions! Questions that I didn't think of asking!
Do you _teach_ the subject?
Because you seem to know possible questions students will ask.
Thank you very much for this video!
Nope - I am not a teacher - I'm just familiar with the common questions that people might ask.
Thanks for this. I am measuring AC current and feeding a 12bit adc so this was essential for my passive cct conditioning.
Great tutorial as always, Alan. Thank you.
Great delivery and information. I appreciate your ability to share the knowledge you have in a logical, easy to understand manner. Keep up the great work. By the way, I decided to subscribe. Thank you.
12:50 "And you plug it in, ... boom ..." Boom??? Reallly??? :-)
But in general, there is a (small) perturbation near their zero, though.
Good, very good, video. Second point, if the op amp has its offset not defined as being the earth ground we have to adjust the + and - signal with respect to the same zero origine... which can then be THE real headhake.
I really hope everything is fine on your side, it is 2021 here!
Beautiful tutorial! Thanks!
Thank you very much sir... hooking up the oscilloscope really helped understanding the virtual ground!
Very VERY good Sir! Thank you!
Another excellent video. Thank you for taking the time to make these, as they are very helpful to me.
Very nice and easy to grasp presentation - thank you!
Thank you Alan, you have such a great way of explaining things.
Thanks so much for the explanation! Now I understand why my circuit wasn't behaving as I expected :P
you're the cutest
Super useful!
Great explanation Alan... always enjoy your videos
older amplifiers used transformer less power transformers, it was called hot chassis which didn't use an AC power transformer but a series of tube filaments to step down the AC voltage. I'm not sure how tube filaments step down an AC voltage, but many you might know. On the schematics it looks like 4 to 6 filaments stepping down 120VAC to 40VAC for the rectifier tube.
The filaments are simply resistive elements - so there's a I*R voltage drop across each one in series.
As always, a great video Alan- perhaps in a future installment you may touch on the areas of device types (e.g. bipolar vs MOSFET) and how that affects ability to drive near the rails, slew rate (speed) considerations (e.g. why use a bipolar op-amp vs MOSFET for speed), etc. Great little tutorial with very nice demonstrations. 73 Bill N4BKT
Thank you so much or this excellent video which clear out some confusion on the rail to rail and split supplies concepts. I can't wait to see more OP-AMP tutorials (if you have more coming).
Thanks for the great information😊
Excellent presentation. Thank you.
Even if this is stuff I already knew I have fun listening to your explanations (plus I always learn something new!) :)
Thank you for your work, and the didactic excellent Hand-draw sheets via the
review of the Data-Sheets. keep on .
It will help me a lot.
Another informative and interesting video. Thanks Alan.
Thank you for taking the time,- very enlightening.
Great demonstration and explanation; you make it very intuitive. 73 de AI4SV Jack
Very nice tutorial. Thank you!
Great Job! Clear and concise.
Good video!
Great demo!
great stuff as always
thank you for the awesome video alan
thank you. very helpful
Thank you! This is very informative!
Thanks. Very informative.
This video is so damn good, thank you!
Another very good video Alan. Could it be possible to show your power supplies setup and signal generator and earthing arrangements, many thanks.
The schematic on the last page of my notes is accurate. In my case, the signal generator features a floating output (the shell of the BNC isn't grounded), so I was able to put it in series with the supply that I used to adjust the offset.
so many wonderful toys
Well, from my interpretation, what you're calling a "virtual ground" is just a voltage reference. You could also call it an "ac ground" because of the very small shunt impedance due to the capacitor. The actual virtual ground exists on the "-" input, not the "+".
Great stuff! Thanks!
Thanks for the great information. I was, however, hoping to learn a bit about how to calculate the power consumption of the op-amp. So.. if the output feeds say an ADC, how do we calculate the power loss through the gain resistors and the chip itself. Once again, great tutorial. Thanks.
It should be noted that the output can be isolated through a capacitor to remove the dc portion of the waveform.
Well done!
What is the most effective method to bias the op amp using single power supply? Would it be split resistive or using other means? Thank you for your great to the point presentation!
resistor divider is certainly most common, but it really depends on the application.
nice video
At around the 2 minute mark, I don't think that point should be called virtual ground, unless it's a term that is used pretty loosely. Virtual ground for the op-amp would be there when you have the positive terminal connected to GND and negative feedback configuration, where the feedback action is trying to make the voltage at the negative op-amp input equal to the voltage at the positive input. In the circuit shown at the 2 minute mark, it looks like an open loop.
thanks a lot, great videos
If my question was answered 9 years after the video was published the question would be out of what is indicated below:
Suppose your using a little module using a lm358 IC that was purchased out of China and pre-assembled to serve as a Mic or transducer preamp as I expect to use mine. Suppose the module has four pins with one for input from a signal source, one for output of signal from the lm358 and two pins for power supply.
Suppose you do as I did which is connect two 4 pack AA battery packs in series and supply power to the module with the free end of the one battery pack leading to Vcc and the other free end of the battery pack leading to what one might call Vee on the lm358.
The question then is what would you use as ground or the 0 volt reference point for the input and output signal?
I have used the Virtual Ground created by where the two battery packs are physically connected thus I suppose the signal swings between +6 volts and -6 volts & I have used what leads to what I have called Vee serve as the ground for the signal's input and output and see no difference on my scope under each scheme.
Any comments on this, to me, puzzle would be greatly appreciated.
Assuming you module was designed to be a mic preamp, then the input is most certainly AC coupled, so the ground reference for the signal doesn't really matter - it could be either supply rail or the virtual ground because from an AC standpoint, they're all the same (all shorted together with capacitors.
@@w2aew thanks....
it's very informative..can you upload more videos about other useful op amp applications, like half/full wave rectifiers, differentiator/integrator, window comparator and etc.. tnx
Cheers.
Super useful. Are there some performance tradeoffs to the rail-to-rail opams? Noise, bandwidth, input voltage offset, temperature stability, drive/sink output current, etc.
yes true, I just didn't know that different tube filaments has different resistance values which is a voltage drop. I thought as tube filaments all had the same resistance value.
Thanks for responding. I'll give it a shot :-)
thank you!
But electronic engineers and technicians say that the laminations changes the frequency response of the transformer is this true or false? or do they mean the core material inductance will change value because of the wire winding lamination?
What are the advantages of using Two Diode Full wave rectification compared to using 4 diode bridge full wave rectification? The Two Diode Full wave rectification has benefits how so
Great video, very easy to understand, I am building an audio signal generator and you can use eiher 6 volt sprit or 12 volt single, can you tell me which way to go? Thank you kindly!!
From a circuit performance standpoint, they'll be identical. So, it really comes down to details of your requirements. Do you want the output to be centered around ground and DC coupled? If so, then use a split supply.
Around 1:50 you mention you AC couple the bias to ground "to keep it stable" can you point me in the direction of where I can get some additional information on that? I'm going to guess you mean the capacitor will keep the voltage "less spikey" and closer to a flat line? If that is the case I'd think you'd have to carefully select the cap so it let low frequencies pass but not high ones?
Very interesting video, thank you!!
Also, the number of times you said "okay" drove me absolutely insane, but I had to keep watching :((((
Hi,
we can make an offset on the positive input simply using a resistor divider, but how can we offset the negative input which takes the input signal without using an additional power supply?
thanks
What is the purpose of the 2.2k resistor at 7:30? I’ve seen these before, or even in the feedback loop of unity gain buffers, but never understood what they’re for?
How to make a duel or split supply out of a single power source say a 24dc wall wart?
In old tube amplifiers the 6vac heat voltage the transformer didn't have a center tap for the ground for the 6vac. To convert a non center tap transformer to a 6vac center tap you put two 100 ohm balanced resistors and tie them to a virtual ground which will be the tubes plate voltage. Most plate voltage are from 200vdc to 450vdc. Not sure why they would put the virtual ground to a DC potential connected to the plate voltage so that the 6vac heat voltage will have a virtual ground virtual center tap. Have you heard of this type of virtual ground?
What formula can you use to convert Full wave AC voltage to the Equivalent Half Wave AC voltage and vise versa? Because if a circuit needs 26vac Half wave voltage, how can you convert this to the equivalent Full wave AC voltage?
My question is that you used a variable voltage source to make an offset on both the positive and negative inputs (schematic 7:55), thus your input signal that you want to amplify is floating relative to ground, what if the input signal is not floating? how can i make an offset on the input signal, can i use a voltage divider, what if the input signal source has a very large impedance, should i use a buffer before?
thanks
Can you make a video lesson about measuring power supply rejection ratio and also power supply control loop stability? They make special probes called power rail voltage probe, which i have never used one and don't know how its so much different
I'll add that topic to my list. Power Rail probes are special, wide-bandwidth, low-attenuation probes that allow you to dial-out the supply rail voltage, and concentrate the high sensitivity measurement (maybe 1-2mV/div) around the supply rail (large DC offset).
@@w2aew Back in the 60's and before they used "bootleg grounding schemes" because it was just a 2 prong Floating Earth and not using a 3 prong with an earth ground. When a piece of equipment is wired as "bootleg grounding using a 3 prong cable" ( Not 2 prong ) the DVM meter will be connected to earth ground or circuit ground. When making In-circuit voltage measurements all the voltage measurements are going to be incorrect and wrong because the equipment is wired as bootleg grounding? because when you disconnect the earth ground wire/bootleg ground the in-circuit voltage measurements on the DVM meter are going to be correctly different, any reasons why?
Hi, very instructive video. What is the role of the 2.2k resistor connected to the + input ? The one that has its value in parenthesis, it is seen in the drawing of your example circuit at around 8:00 . Sorry if that question was asked already.
+w2aew I would also like to know why this 2.2k resistor was used.
A resistor is usually used in that location to help minimize offset due to the input bias current of the op amp inputs. The value is usually equal to the parallel combination of the resistors connected to the inverting input, so it *should* be approx 1.4kohms. I used 2.2k simply because it wasn't critical for the video topic, and it was laying around on the bench near the breadboard ;-)
Thanks for the explanation! As far as I understand, since the gain here was less than 1.5, I suppose even this resistor wasn't necessary because the error would have been very small. Nevertheless it is important to know about this stuff. I was able to find a bit more in-depth about this watching EEVblog #479.
for a balanced signal input, where you have a floating differential signal going into the +/- terminals of the opamp, a split supply would be more necessary correct?
Great video. thank you very much.
What happened to output swing voltage if the output current is increased? how to use opamp to drive a low impedance load?
It depends on the specific op amp. In general, the available voltage swing is reduced into low impedance loads. Some op amps can drive low impedance loads better than others. Often times a buffer designed for low-impedance loads (like a push-pull stage) is included in the feedback loop of an op amp to improve the low-impedance drive capability.
@@w2aew Acutally I used push pull or single transistor at the output stage of opamp; it works fine but not efficient. With single supply, the output voltage has the dc offset.
I have a 741 op amp with a 170mV, 852Hz input sine wave, +5/-5V power. I have a 10k resistor from the inverting terminal to ground and a 20k feedback resistor (output to inverting terminal), the input is on the non-inverting terminal ... the gain should be 3... but instead the gain is roughly 1. (So the output is roughly 170mV.) The output is not clipping... I'm not sure what's going on...?
if your opamp circuit with a virtual ground connects to a another opamp that is using a single supply (ex 0-12V), in the gain loop of a non-inverting amplifier, would you connect the resistor to the 0V ground of to the virtual ground?
I have tried measuring the AC line noise on the primary side of various equipment on an oscilloscope but not sure how do it correctly. How can you measure the AC line noise level using an oscilloscope or is it better to use a spectrum analyzer to measure AC line noise? my Fluke DMM meter can't measure the AC line noise level so what meter would do this?