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Stuff copied here from op-amp page in preparation.
Op-amps have applications as artificial neurons in neural nets. Specifically, as a number of summer amplifiers attached to a central amplifier attached to a comparator or schmitt trigger. For details, see http://www.rgu.ac.uk/files/chapter10%20-%20implementing%20ANNs.pdf
The correct term for this cct is Ideal Diode. The term super suggests something thats actually better than a diode. This term super diode is not used in electronics (not that Ive heard of) and should therfore be changed to ideal diode.-- Light current 17:44, 29 September 2005 (UTC)
CAn we change it then to precision rectifier?-- Light current 19:36, 7 October 2005 (UTC)
Yes it is better than a diode. Its ideal but not super-- which would imply-- well Im not sure what it implies. I should have said better somehow than an Ideal diode. The term super as applied to electronics/electrical engineering (apart from superconductor) is outside my professional experience - Light current 22:11, 29 September 2005 (UTC)
THis statement seems to convey very little useful info. I think its wrong anyway. I will delete unless it can be tightened up-- Light current 01:15, 30 September 2005 (UTC)
Expunged useless stuff-- Light current 18:05, 12 October 2005 (UTC)
Addition: Whereas Input-Bias Current is more or less independent from the input voltage difference, it depends on temperature. Neither is output current dependent on the output voltage, as long as the opamp is capable do deliver that current. Therefor, in- and output-impedance are missleading terms in this context; impedance is used to discribe current variation caused by voltage change. This ratio is neither constant for in- nor outputs of opamps. — Preceding unsigned comment added by 83.65.147.83 ( talk) 20:36, 20 November 2012 (UTC)
Generally, we want to cover opamp circuits the way they are used, not as variations of a universal configuration, so I'm not sure these recent edits are that helpful. Maybe you could put something like that in the differential amplifier article, showing the connection between diff amps and all the other varieties? (I did the same thing with a "universal transistor amplifier", and it's not a great idea. See Talk:Common collector, for example.)
Although the use of HTML to represent math in articles is somewhat contentious, using complicated HTML to simulate the same effect as TeX is definitely bad, and mixing both within the same equation is very bad. Can you restore them to TeX? — Omegatron 04:16, 2 November 2005 (UTC)
In some other encyclopedias this material is splitted into several articles. To generate cross-language links, the header references are used (for instance, . Please avoid changing the headers without the real need. Audriusa 20:38, 2 January 2006 (UTC)
en:Operational amplifier applications#Differentiator
We should include Breakpoint generators here.-- HappyEater 16:40, 19 May 2007 (UTC)
In the explanation for the non-inverting amp, the resistor subscripts don't correspond to the picture. "A third resistor, of value R_\mathrm{f} \| R_\mathrm{in}, added between the Vin source and the non-inverting input, while not necessary, minimizes errors due to input bias currents."
I looked everywhere for what the contributor meant by "R1||R2" and couldn't find any references besides: 'parallel-to' in geometry; and a logical OR operator in C programming. I don't think it means either of those and might possibly be a typo for "R1/R2". This needs to be verified by someone with more knowledge than myself.
I have often noticed a tendency to confusion around this term. I believe the usage is to call this circuit with an opamp and two matched pairs of resistors, a "Difference Amplifier". "Differential Amplifier" is the term used to name the input stage inside the opamp, as you will see if you follow the link to that article. Friendly Person ( talk) 13:31, 19 June 2008 (UTC)
If a fig is not provided for the "Zero level detector" "section", the section should be removed. — TedPavlic ( talk) 14:35, 26 January 2009 (UTC)
The diagram for this is incorrect. One of the input buffer amplifiers has the '+' and '-' inputs transposed. 20.133.0.13 ( talk) 13:37, 17 February 2009 (UTC)
Sorry, I have removed the link to the page about Philbrick absolutely involuntarily. I have no idea how it has happened and I was unpleasantly surprised when I saw Zen-in's remark. Philbrick is a legend; I highly appreciate his achievements. Circuit-fantasist ( talk) 15:35, 20 March 2009 (UTC)
There is currently a page dedicated to the inverting amplifier configuration of the op amp. The page doesn't seem to add much value beyond what is already in Operational amplifier applications or Operational amplifier. Merge? Scottr9 ( talk) 14:41, 23 April 2009 (UTC)
There is an orphaned Log_amplifier page. The quality of that page is awful, but I would suggest actually keeping it and merging it with the Logarithmic Output from this page (and hopefully improving the content of the log amp page!).
Thus, Logarithmic output would have it's own main page and the section in this page could be excerpted from that article. This would be similar to how the Operational_amplifier_applications#Precision_rectifier section is handled with the Precision_rectifier main page.
Furthermore, something should be done to connect the Logarithmic_video_amplifier page.
Marangu ( talk) 13:21, 21 May 2009 (UTC)
The text on power supply design contained some very odd wording that I regard as meaningless. I have edited to remove the offending text, but if anyone can supply a meaningful alternative then please insert. —Preceding unsigned comment added by 86.53.81.124 ( talk) 16:52, 28 December 2009 (UTC)
The role of the op-amp in this circuit is to compensate the voltage drop across the capacitor. For this purpose, the op-amp adds so much voltage to the input voltage as it loses across the capacitor. The properly supplied op-amp acts as a compensating voltage source connected in series to the capacitor and the input voltage source.
This idea may be generalized for all the op-amp inverting circuits with parallel negative feedback (e.g., Inverting amplifier, Summing amplifier, Differentiator, Logarithmic output, Exponential output from this page). In all these circuits the op-amp compensates the voltage drop across the element connected between the output and the inverting input by adding the same voltage to the input voltage as it loses across this element. See also Voltage Compensation. Circuit dreamer ( talk) 18:38, 30 March 2010 (UTC)
Regarding to the sign of the feedback, there are two kinds of circuits with feedback - circuits with negative feedback (e.g., inverting and non-inverting amplifier) and circuits with positive feedback (e.g., non-inverting and inverting Schmitt trigger).
Regarding to the way of feedback applying, there are two kinds of circuits with feedback - circuits with parallel feedback (inverting amplifier and non-inverting Schmitt trigger) and circuits with series feedback (non-inverting amplifier and inverting Schmitt trigger).
In circuits with parallel feedback (look at the picture of the inverting amplifier above and at the picture of the non-inverting Schmitt trigger here), the op-amp's output and the input voltage source are connected through the feedback circuit (the resistors R1 and R2). As a result, the op-amp passes a current through the input source; so, the circuit impacts the input source. Note that in circuits with parallel negative feedback (inverting amplifier) the two voltage sources are connected in the same direction travelling through the circuit; so their voltages are added; in circuits with parallel positive feedback (non-inverting Schmitt trigger) the two voltage sources are connected in the opposite direction; so their voltages are subtracted. Now look at the circuit of NIC (more precisely, it is a VNIC) that is a typical S-shaped negative resistor, and you will see the same phenomenon there - the op-amp's output and the input voltage source are connected through the positive feedback circuit (the resistors R3 and the internal resistor of the input source Vs). That is why the non-inverting Schmitt trigger behaves as a (an S-shaped) negative resistor. See also Linear Mode of Current Inversion NIC and Bistable Mode of Current Inversion NIC.
In circuits with series feedback (look at the picture of the non-inverting amplifier above and at the picture of the inverting Schmitt trigger here), there is no connection between the op-amp's output and the input voltage source. So, no current flows between them and these circuits do not possess a negative resistance; they have extremely high input resistance. Circuit dreamer ( talk) 20:33, 30 March 2010 (UTC)
As of today (April 16, 2010), both of the Schmitt trigger versions seem clearly wrong. Both need a third resistor, to establish a resistor-divider between +5v and ground. As they stand now, without the third resistor, they are merely variations of the inverting and non-inverting amplifiers. —Preceding unsigned comment added by 63.207.173.11 ( talk) 20:35, 16 April 2010 (UTC)
(outdent) There is a lot of confused maths being thrown about here! Put simply, we have:
Whichever way you look at it, as soon as Vin becomes non-zero, Vout will initially tend in the same direction. As the feedback is positive, this will only pull the circuit further away from the solution to these equations (Vout/Vin = A/(2 - A) ≈ -1). Therefore, this solution is not stable. In other words, the only stable states of this circuit are with the output saturated at one of the rails. Oli Filth( talk| contribs) 00:27, 18 April 2010 (UTC)
Of course, circuits can be and have to be analyzed by formal methods but first basic ideas behind them have to be shown. At this first stage, mathematical expressions will not help us to grasp circuit ideas; they can't explain circuits. Formal methods will not answer all WHAT and HOW questions needed (what a problem electronic components solve, why they are connected there, what they actually do in circuits, how they do what they do, etc.) as they are quantitative tools while circuit ideas are something qualitative. It is more than obvious that we have to explain qualitative things by qualitative tools and quantitative things by quantitative tools. It is a great mistake to explain qualitative things by quantitative tools; at this stage, quantitative tools can serve only as secondary means.
Do not forget that these circuits have seen the light of day thanks to human fantasy, imagination and enthusiasm. We, human beings, understand, explain and even invent circuits by using our human intuition, imagination and emotions and only then we analyze, calculate and design them by using our reason, mind and intelligence. Circuits are systems of subsystems (functional blocks or more-elementary circuits consisting of components connected according to some clever idea). In order to understand/explain complex circuits, we have to discern/show these functional blocks (the basic op-amp circuits described in this page). For this purpose, we have to have very good notion about them.
Every, even the most elementary circuit solution, is based on some fundamental idea. When we see a new circuit and we try to understand it, we need to know this idea, the clever trick on which the circuit is based. Our page visitors need too the fundamental circuit ideas and concepts to understand circuits.
In this current state, the article does not show the concepts behind op-amp applications. That is why, I would like to insert some text (two-three sentences) in the beginning of every op-amp application (subsection) where to show the basic idea. Some groups of circuits are based on the same general idea that may be shown in the beginning of the group. The problem is that now the op-amp circuits are classified only according to linearity. With the same success they may be classified by the presence of the feedback (without or with), by the kind of the feedback (negative or positive), by the way of feedback applying (parallel or series), etc. But the page will become too branched. So, I suggest to show (where it is possible) the general idea in the beginning of the common sections and to show the specific implementation in the beginning of the concrete subsections.
Circuit dreamer ( talk) 14:35, 2 April 2010 (UTC)
I have restored the link to voltage compensation as the module is closely related to the topic. It considers op-amp inverting circuits with negative feedback (op-amp circuits with parallel negative feedback). Six of all the 18 op-amp circuits (1/3) are that sort of circuits: inverting amplifier, summing amplifier, integrator, differentiator, log converter and antilog converter.
In the beginning, the basic idea behind this kind of circuits is shown by step-by-step building scenario. Then, total of 8 op-amp circuits are considered thoroughly in the wikibooks module: inverting amplifier, capacitive integrator, capacitive differentiator, inductive integrator, inductive differentiator, log converter, antilog converter. The circuits are accompanied by informative time diagrams. Circuit dreamer ( talk, contribs, email) 12:31, 28 April 2010 (UTC)
I have placed a link to the applications section of Miller theorem as ten circuits with modified impedance belonging to op-amp applications article are closely related to Miller theorem. Here is the list of these circuits.
Circuit dreamer ( talk, contribs, email) 17:50, 5 August 2010 (UTC)
Although I have taken the trouble to list the 10 op-amp circuits from this page closely related to Miller theorem, the link on the main article was deleted without any explanations why. I have restored the link because the fact that 10 of the total 17 circuits (60%) are related to Miller theorem is a good reason to place a link to it. Circuit dreamer ( talk, contribs, email) 18:27, 6 August 2010 (UTC)
I just cleaned up (I think) some commentary at the section on the "Inverting differentiator", but I'm not sure why it's there. The commentary isn't about issues implementing differentiators with operational amplifiers. Instead, it's about using differentiators in larger feedback loops. This may be a topic of interest, but it probably doesn't belong on this page and probably deserves a richer discussion. So should it be removed? Shouldn't this page just give the outline of the implementation of an OA-based inverting differentiator? — TedPavlic ( talk/ contrib/ @) 15:57, 12 July 2011 (UTC)
Zero crossing threshold detector duplicates a section here and should be merged for context. -- Wtshymanski ( talk) 22:03, 28 November 2011 (UTC)
I have edited section "Inverting Integrator" to incorporate much of article Op amp integrator, per the suggestion in the banner at the beginning of this section. I have not attempted to merge in that article's section "Frequency response" nor "Applications" nor its reference. This work is a first cut and needs to include the derivation of the transfer function for each of the two circuits and it needs to include substantiation for the statement about the value of Rn.
I read the discussion above, titled "About the op-amp inverting integrator" and gave thought to how the concerns voiced there bore on the section. I hope I have addressed them reasonably well. ArthurOgawa ( talk) 09:01, 24 February 2014 (UTC)
Since Wikipedia is suppose to be helpful for "newbies", an important topic seems to be missing from this article and its parent operational amplifier article, which is how to properly terminate unused op-amps. I'm not sure which article it belongs, but I think a section should be created to address this important design issue, including the need for a drawing similar to "this drawing" which came from "this article". Please discuss and someone please add to the correct article. Thanks! • Sbmeirow • Talk • 16:09, 24 July 2014 (UTC)
I wonder if someone could add the current-to-voltage converter configuration to this page? I was surprised to come here and not find it.
It's described here: /info/en/?search=Transimpedance_amplifier
For what it's worth, it's the fourth one on the corresponding french wikipedia page: http://fr.wikipedia.org/wiki/Montages_de_base_de_l%27amplificateur_op%C3%A9rationnel "Convertisseur courant à tension" = "Converter of current to voltage". Gwideman ( talk) 19:03, 29 April 2015 (UTC)
1. Under the logarithmic and the exponential sections, why are input and output voltage written as vin and vout instead of Vin and Vout? Are they small signal? I don't think they are.
2. Also, I've been trying to verify . If I use R=1 kΩ, Is=14.11e-9 A, Vin=1 V, I get -3.321e12 V. How is that possible? There must be something wrong. I think the extinction coefficient (n) should also be added for accuracy, including in the equation for the logarithmic output (VT should really be nVT).
ICE77 ( talk) 08:56, 4 August 2015 (UTC)
Laogeodritt, thanks for the feedback.
1. I made the changes and they are live now.
2. After looking at the exponential increase of even small input voltages I have to agree that an output of 1V is unrealistic so that's why I got a huge output voltage. Clearly, the output would be clipped to near the lower supply rail. My simulation actually produces -13.77V at the output with an input of 1V and rails of ±15V. The extinction coefficient I have in my simulation is 1.984. It clearly needs to be included in the equation and it simply modifies the classic Schockley equation. If you don't include it, it's not practical. I would include it in the equations. After stepping the voltage from 0V to 1V in 100mV increments I noticed that the equation matches the simulation up to 300mV but then the equation diverges way too far when compared to the simulated values. I wonder what is the reason behind that. I also wonder what is a practical input voltage for the circuit in an actual application.
ICE77 ( talk) 05:21, 14 August 2015 (UTC)
Most of Japanese engineers still believe the term for "virtual short" should be "imaginary short" instead, because of a ridiculous textbook written in 1973, the famous author of which primarily told "imaginal short" which was later corrected to "imaginary short" for the grammatical sense. Nowadays, most Japanese engineers still believe it should be "imaginary" instead of "virtual" because their teachers never corrected the term who treated the textbook as "bible". It may seem nonsense, but translated Japanese terms apparently share the same meaning and thus they cannot understand the difference. So, er, is it okay to add "imaginary" in explanation with some historical description above? -- Wordmasterexpress ( talk) 06:13, 9 October 2015 (UTC)
I have moved most html comments ( WP:HIDDEN) from the article to here for consideration. It is not satisfactory for the article to retain these long-term, and the material looks to be too "tutorial" in nature for an encyclopedic article.
An inverting amplifier inverts and scales the input signal. As long as the op-amp gain is very large, the amplifier gain is determined by two stable external resistors (the feedback resistor Rf and the input resistor Rin) and not by op-amp parameters which are highly temperature dependent. In particular, the Rin–Rf resistor network acts as an electronic seesaw (i.e., a class-1 lever) where the inverting (i.e., −) input of the operational amplifier is like a fulcrum about which the seesaw pivots. That is, because the operational amplifier is in a negative-feedback configuration, its internal high gain effectively fixes the inverting (i.e., −) input at the same 0 V (ground) voltage of the non-inverting (i.e., +) input, which is similar to the stiff mechanical support provided by the fulcrum of the seesaw. Continuing the analogy,
Hence, the amplifier output is related to the input as in
So the voltage gain of the amplifier is where the negative sign is a convention indicating that the output is negated. For example, if Rf is 10 kΩ and Rin is 1 kΩ, then the gain is −10 kΩ/1 kΩ, or −10 (or −10 V/V). [1] Moreover, the input impedance of the device is because the operational amplifier's inverting (i.e., −) input is a virtual ground.
In a real operational amplifier, the current into its two inputs is small but non-zero (e.g., due to input bias currents). The current into the inverting (i.e., −) input of the operational amplifier is drawn across the Rin and Rf resistors in parallel, which appears like a small parasitic voltage difference between the inverting (i.e., −) and non-inverting (i.e., +) inputs of the operational amplifier. To mitigate this practical problem, a third resistor of value can be added between the non-inverting (i.e., +) input and the true ground. [2] This resistor does not affect the idealized operation of the device because no current enters the ideal non-inverting input. However, in the practical case, if input currents are roughly equivalent, the voltage added at the inverting input will match the voltage at the non-inverting input, and so this common-mode signal will be ignored by the operational amplifier (which operates on differences between its inputs).
Amplifies a voltage (multiplies by a constant greater than 1)
References
I left the following two comments (shown in green here) for later investigation:
correction to come—ArthurOgawa
should link directly to TI
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Stuff copied here from op-amp page in preparation.
Op-amps have applications as artificial neurons in neural nets. Specifically, as a number of summer amplifiers attached to a central amplifier attached to a comparator or schmitt trigger. For details, see http://www.rgu.ac.uk/files/chapter10%20-%20implementing%20ANNs.pdf
The correct term for this cct is Ideal Diode. The term super suggests something thats actually better than a diode. This term super diode is not used in electronics (not that Ive heard of) and should therfore be changed to ideal diode.-- Light current 17:44, 29 September 2005 (UTC)
CAn we change it then to precision rectifier?-- Light current 19:36, 7 October 2005 (UTC)
Yes it is better than a diode. Its ideal but not super-- which would imply-- well Im not sure what it implies. I should have said better somehow than an Ideal diode. The term super as applied to electronics/electrical engineering (apart from superconductor) is outside my professional experience - Light current 22:11, 29 September 2005 (UTC)
THis statement seems to convey very little useful info. I think its wrong anyway. I will delete unless it can be tightened up-- Light current 01:15, 30 September 2005 (UTC)
Expunged useless stuff-- Light current 18:05, 12 October 2005 (UTC)
Addition: Whereas Input-Bias Current is more or less independent from the input voltage difference, it depends on temperature. Neither is output current dependent on the output voltage, as long as the opamp is capable do deliver that current. Therefor, in- and output-impedance are missleading terms in this context; impedance is used to discribe current variation caused by voltage change. This ratio is neither constant for in- nor outputs of opamps. — Preceding unsigned comment added by 83.65.147.83 ( talk) 20:36, 20 November 2012 (UTC)
Generally, we want to cover opamp circuits the way they are used, not as variations of a universal configuration, so I'm not sure these recent edits are that helpful. Maybe you could put something like that in the differential amplifier article, showing the connection between diff amps and all the other varieties? (I did the same thing with a "universal transistor amplifier", and it's not a great idea. See Talk:Common collector, for example.)
Although the use of HTML to represent math in articles is somewhat contentious, using complicated HTML to simulate the same effect as TeX is definitely bad, and mixing both within the same equation is very bad. Can you restore them to TeX? — Omegatron 04:16, 2 November 2005 (UTC)
In some other encyclopedias this material is splitted into several articles. To generate cross-language links, the header references are used (for instance, . Please avoid changing the headers without the real need. Audriusa 20:38, 2 January 2006 (UTC)
en:Operational amplifier applications#Differentiator
We should include Breakpoint generators here.-- HappyEater 16:40, 19 May 2007 (UTC)
In the explanation for the non-inverting amp, the resistor subscripts don't correspond to the picture. "A third resistor, of value R_\mathrm{f} \| R_\mathrm{in}, added between the Vin source and the non-inverting input, while not necessary, minimizes errors due to input bias currents."
I looked everywhere for what the contributor meant by "R1||R2" and couldn't find any references besides: 'parallel-to' in geometry; and a logical OR operator in C programming. I don't think it means either of those and might possibly be a typo for "R1/R2". This needs to be verified by someone with more knowledge than myself.
I have often noticed a tendency to confusion around this term. I believe the usage is to call this circuit with an opamp and two matched pairs of resistors, a "Difference Amplifier". "Differential Amplifier" is the term used to name the input stage inside the opamp, as you will see if you follow the link to that article. Friendly Person ( talk) 13:31, 19 June 2008 (UTC)
If a fig is not provided for the "Zero level detector" "section", the section should be removed. — TedPavlic ( talk) 14:35, 26 January 2009 (UTC)
The diagram for this is incorrect. One of the input buffer amplifiers has the '+' and '-' inputs transposed. 20.133.0.13 ( talk) 13:37, 17 February 2009 (UTC)
Sorry, I have removed the link to the page about Philbrick absolutely involuntarily. I have no idea how it has happened and I was unpleasantly surprised when I saw Zen-in's remark. Philbrick is a legend; I highly appreciate his achievements. Circuit-fantasist ( talk) 15:35, 20 March 2009 (UTC)
There is currently a page dedicated to the inverting amplifier configuration of the op amp. The page doesn't seem to add much value beyond what is already in Operational amplifier applications or Operational amplifier. Merge? Scottr9 ( talk) 14:41, 23 April 2009 (UTC)
There is an orphaned Log_amplifier page. The quality of that page is awful, but I would suggest actually keeping it and merging it with the Logarithmic Output from this page (and hopefully improving the content of the log amp page!).
Thus, Logarithmic output would have it's own main page and the section in this page could be excerpted from that article. This would be similar to how the Operational_amplifier_applications#Precision_rectifier section is handled with the Precision_rectifier main page.
Furthermore, something should be done to connect the Logarithmic_video_amplifier page.
Marangu ( talk) 13:21, 21 May 2009 (UTC)
The text on power supply design contained some very odd wording that I regard as meaningless. I have edited to remove the offending text, but if anyone can supply a meaningful alternative then please insert. —Preceding unsigned comment added by 86.53.81.124 ( talk) 16:52, 28 December 2009 (UTC)
The role of the op-amp in this circuit is to compensate the voltage drop across the capacitor. For this purpose, the op-amp adds so much voltage to the input voltage as it loses across the capacitor. The properly supplied op-amp acts as a compensating voltage source connected in series to the capacitor and the input voltage source.
This idea may be generalized for all the op-amp inverting circuits with parallel negative feedback (e.g., Inverting amplifier, Summing amplifier, Differentiator, Logarithmic output, Exponential output from this page). In all these circuits the op-amp compensates the voltage drop across the element connected between the output and the inverting input by adding the same voltage to the input voltage as it loses across this element. See also Voltage Compensation. Circuit dreamer ( talk) 18:38, 30 March 2010 (UTC)
Regarding to the sign of the feedback, there are two kinds of circuits with feedback - circuits with negative feedback (e.g., inverting and non-inverting amplifier) and circuits with positive feedback (e.g., non-inverting and inverting Schmitt trigger).
Regarding to the way of feedback applying, there are two kinds of circuits with feedback - circuits with parallel feedback (inverting amplifier and non-inverting Schmitt trigger) and circuits with series feedback (non-inverting amplifier and inverting Schmitt trigger).
In circuits with parallel feedback (look at the picture of the inverting amplifier above and at the picture of the non-inverting Schmitt trigger here), the op-amp's output and the input voltage source are connected through the feedback circuit (the resistors R1 and R2). As a result, the op-amp passes a current through the input source; so, the circuit impacts the input source. Note that in circuits with parallel negative feedback (inverting amplifier) the two voltage sources are connected in the same direction travelling through the circuit; so their voltages are added; in circuits with parallel positive feedback (non-inverting Schmitt trigger) the two voltage sources are connected in the opposite direction; so their voltages are subtracted. Now look at the circuit of NIC (more precisely, it is a VNIC) that is a typical S-shaped negative resistor, and you will see the same phenomenon there - the op-amp's output and the input voltage source are connected through the positive feedback circuit (the resistors R3 and the internal resistor of the input source Vs). That is why the non-inverting Schmitt trigger behaves as a (an S-shaped) negative resistor. See also Linear Mode of Current Inversion NIC and Bistable Mode of Current Inversion NIC.
In circuits with series feedback (look at the picture of the non-inverting amplifier above and at the picture of the inverting Schmitt trigger here), there is no connection between the op-amp's output and the input voltage source. So, no current flows between them and these circuits do not possess a negative resistance; they have extremely high input resistance. Circuit dreamer ( talk) 20:33, 30 March 2010 (UTC)
As of today (April 16, 2010), both of the Schmitt trigger versions seem clearly wrong. Both need a third resistor, to establish a resistor-divider between +5v and ground. As they stand now, without the third resistor, they are merely variations of the inverting and non-inverting amplifiers. —Preceding unsigned comment added by 63.207.173.11 ( talk) 20:35, 16 April 2010 (UTC)
(outdent) There is a lot of confused maths being thrown about here! Put simply, we have:
Whichever way you look at it, as soon as Vin becomes non-zero, Vout will initially tend in the same direction. As the feedback is positive, this will only pull the circuit further away from the solution to these equations (Vout/Vin = A/(2 - A) ≈ -1). Therefore, this solution is not stable. In other words, the only stable states of this circuit are with the output saturated at one of the rails. Oli Filth( talk| contribs) 00:27, 18 April 2010 (UTC)
Of course, circuits can be and have to be analyzed by formal methods but first basic ideas behind them have to be shown. At this first stage, mathematical expressions will not help us to grasp circuit ideas; they can't explain circuits. Formal methods will not answer all WHAT and HOW questions needed (what a problem electronic components solve, why they are connected there, what they actually do in circuits, how they do what they do, etc.) as they are quantitative tools while circuit ideas are something qualitative. It is more than obvious that we have to explain qualitative things by qualitative tools and quantitative things by quantitative tools. It is a great mistake to explain qualitative things by quantitative tools; at this stage, quantitative tools can serve only as secondary means.
Do not forget that these circuits have seen the light of day thanks to human fantasy, imagination and enthusiasm. We, human beings, understand, explain and even invent circuits by using our human intuition, imagination and emotions and only then we analyze, calculate and design them by using our reason, mind and intelligence. Circuits are systems of subsystems (functional blocks or more-elementary circuits consisting of components connected according to some clever idea). In order to understand/explain complex circuits, we have to discern/show these functional blocks (the basic op-amp circuits described in this page). For this purpose, we have to have very good notion about them.
Every, even the most elementary circuit solution, is based on some fundamental idea. When we see a new circuit and we try to understand it, we need to know this idea, the clever trick on which the circuit is based. Our page visitors need too the fundamental circuit ideas and concepts to understand circuits.
In this current state, the article does not show the concepts behind op-amp applications. That is why, I would like to insert some text (two-three sentences) in the beginning of every op-amp application (subsection) where to show the basic idea. Some groups of circuits are based on the same general idea that may be shown in the beginning of the group. The problem is that now the op-amp circuits are classified only according to linearity. With the same success they may be classified by the presence of the feedback (without or with), by the kind of the feedback (negative or positive), by the way of feedback applying (parallel or series), etc. But the page will become too branched. So, I suggest to show (where it is possible) the general idea in the beginning of the common sections and to show the specific implementation in the beginning of the concrete subsections.
Circuit dreamer ( talk) 14:35, 2 April 2010 (UTC)
I have restored the link to voltage compensation as the module is closely related to the topic. It considers op-amp inverting circuits with negative feedback (op-amp circuits with parallel negative feedback). Six of all the 18 op-amp circuits (1/3) are that sort of circuits: inverting amplifier, summing amplifier, integrator, differentiator, log converter and antilog converter.
In the beginning, the basic idea behind this kind of circuits is shown by step-by-step building scenario. Then, total of 8 op-amp circuits are considered thoroughly in the wikibooks module: inverting amplifier, capacitive integrator, capacitive differentiator, inductive integrator, inductive differentiator, log converter, antilog converter. The circuits are accompanied by informative time diagrams. Circuit dreamer ( talk, contribs, email) 12:31, 28 April 2010 (UTC)
I have placed a link to the applications section of Miller theorem as ten circuits with modified impedance belonging to op-amp applications article are closely related to Miller theorem. Here is the list of these circuits.
Circuit dreamer ( talk, contribs, email) 17:50, 5 August 2010 (UTC)
Although I have taken the trouble to list the 10 op-amp circuits from this page closely related to Miller theorem, the link on the main article was deleted without any explanations why. I have restored the link because the fact that 10 of the total 17 circuits (60%) are related to Miller theorem is a good reason to place a link to it. Circuit dreamer ( talk, contribs, email) 18:27, 6 August 2010 (UTC)
I just cleaned up (I think) some commentary at the section on the "Inverting differentiator", but I'm not sure why it's there. The commentary isn't about issues implementing differentiators with operational amplifiers. Instead, it's about using differentiators in larger feedback loops. This may be a topic of interest, but it probably doesn't belong on this page and probably deserves a richer discussion. So should it be removed? Shouldn't this page just give the outline of the implementation of an OA-based inverting differentiator? — TedPavlic ( talk/ contrib/ @) 15:57, 12 July 2011 (UTC)
Zero crossing threshold detector duplicates a section here and should be merged for context. -- Wtshymanski ( talk) 22:03, 28 November 2011 (UTC)
I have edited section "Inverting Integrator" to incorporate much of article Op amp integrator, per the suggestion in the banner at the beginning of this section. I have not attempted to merge in that article's section "Frequency response" nor "Applications" nor its reference. This work is a first cut and needs to include the derivation of the transfer function for each of the two circuits and it needs to include substantiation for the statement about the value of Rn.
I read the discussion above, titled "About the op-amp inverting integrator" and gave thought to how the concerns voiced there bore on the section. I hope I have addressed them reasonably well. ArthurOgawa ( talk) 09:01, 24 February 2014 (UTC)
Since Wikipedia is suppose to be helpful for "newbies", an important topic seems to be missing from this article and its parent operational amplifier article, which is how to properly terminate unused op-amps. I'm not sure which article it belongs, but I think a section should be created to address this important design issue, including the need for a drawing similar to "this drawing" which came from "this article". Please discuss and someone please add to the correct article. Thanks! • Sbmeirow • Talk • 16:09, 24 July 2014 (UTC)
I wonder if someone could add the current-to-voltage converter configuration to this page? I was surprised to come here and not find it.
It's described here: /info/en/?search=Transimpedance_amplifier
For what it's worth, it's the fourth one on the corresponding french wikipedia page: http://fr.wikipedia.org/wiki/Montages_de_base_de_l%27amplificateur_op%C3%A9rationnel "Convertisseur courant à tension" = "Converter of current to voltage". Gwideman ( talk) 19:03, 29 April 2015 (UTC)
1. Under the logarithmic and the exponential sections, why are input and output voltage written as vin and vout instead of Vin and Vout? Are they small signal? I don't think they are.
2. Also, I've been trying to verify . If I use R=1 kΩ, Is=14.11e-9 A, Vin=1 V, I get -3.321e12 V. How is that possible? There must be something wrong. I think the extinction coefficient (n) should also be added for accuracy, including in the equation for the logarithmic output (VT should really be nVT).
ICE77 ( talk) 08:56, 4 August 2015 (UTC)
Laogeodritt, thanks for the feedback.
1. I made the changes and they are live now.
2. After looking at the exponential increase of even small input voltages I have to agree that an output of 1V is unrealistic so that's why I got a huge output voltage. Clearly, the output would be clipped to near the lower supply rail. My simulation actually produces -13.77V at the output with an input of 1V and rails of ±15V. The extinction coefficient I have in my simulation is 1.984. It clearly needs to be included in the equation and it simply modifies the classic Schockley equation. If you don't include it, it's not practical. I would include it in the equations. After stepping the voltage from 0V to 1V in 100mV increments I noticed that the equation matches the simulation up to 300mV but then the equation diverges way too far when compared to the simulated values. I wonder what is the reason behind that. I also wonder what is a practical input voltage for the circuit in an actual application.
ICE77 ( talk) 05:21, 14 August 2015 (UTC)
Most of Japanese engineers still believe the term for "virtual short" should be "imaginary short" instead, because of a ridiculous textbook written in 1973, the famous author of which primarily told "imaginal short" which was later corrected to "imaginary short" for the grammatical sense. Nowadays, most Japanese engineers still believe it should be "imaginary" instead of "virtual" because their teachers never corrected the term who treated the textbook as "bible". It may seem nonsense, but translated Japanese terms apparently share the same meaning and thus they cannot understand the difference. So, er, is it okay to add "imaginary" in explanation with some historical description above? -- Wordmasterexpress ( talk) 06:13, 9 October 2015 (UTC)
I have moved most html comments ( WP:HIDDEN) from the article to here for consideration. It is not satisfactory for the article to retain these long-term, and the material looks to be too "tutorial" in nature for an encyclopedic article.
An inverting amplifier inverts and scales the input signal. As long as the op-amp gain is very large, the amplifier gain is determined by two stable external resistors (the feedback resistor Rf and the input resistor Rin) and not by op-amp parameters which are highly temperature dependent. In particular, the Rin–Rf resistor network acts as an electronic seesaw (i.e., a class-1 lever) where the inverting (i.e., −) input of the operational amplifier is like a fulcrum about which the seesaw pivots. That is, because the operational amplifier is in a negative-feedback configuration, its internal high gain effectively fixes the inverting (i.e., −) input at the same 0 V (ground) voltage of the non-inverting (i.e., +) input, which is similar to the stiff mechanical support provided by the fulcrum of the seesaw. Continuing the analogy,
Hence, the amplifier output is related to the input as in
So the voltage gain of the amplifier is where the negative sign is a convention indicating that the output is negated. For example, if Rf is 10 kΩ and Rin is 1 kΩ, then the gain is −10 kΩ/1 kΩ, or −10 (or −10 V/V). [1] Moreover, the input impedance of the device is because the operational amplifier's inverting (i.e., −) input is a virtual ground.
In a real operational amplifier, the current into its two inputs is small but non-zero (e.g., due to input bias currents). The current into the inverting (i.e., −) input of the operational amplifier is drawn across the Rin and Rf resistors in parallel, which appears like a small parasitic voltage difference between the inverting (i.e., −) and non-inverting (i.e., +) inputs of the operational amplifier. To mitigate this practical problem, a third resistor of value can be added between the non-inverting (i.e., +) input and the true ground. [2] This resistor does not affect the idealized operation of the device because no current enters the ideal non-inverting input. However, in the practical case, if input currents are roughly equivalent, the voltage added at the inverting input will match the voltage at the non-inverting input, and so this common-mode signal will be ignored by the operational amplifier (which operates on differences between its inputs).
Amplifies a voltage (multiplies by a constant greater than 1)
References
I left the following two comments (shown in green here) for later investigation:
correction to come—ArthurOgawa
should link directly to TI