Talk:Transimpedance amplifier: Difference between revisions
Constant314 (talk | contribs) →Transimpedance amplifier gain: Wikipedia is not a reliable source |
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::And by the way, Wikipedia pages are not considered reliable sources.[[User:Constant314|Constant314]] ([[User talk:Constant314|talk]]) 21:09, 10 July 2014 (UTC) |
::And by the way, Wikipedia pages are not considered reliable sources.[[User:Constant314|Constant314]] ([[User talk:Constant314|talk]]) 21:09, 10 July 2014 (UTC) |
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:: No you are wrong about this. Amplification does not require the same units at the input and output. There is no ambiguity in how this is stated in the article. Gain is an important property of TIAs and it is always stated in Ohms. Open any good book on electronics, like the ones I consulted in writing this page, and you will see the terms gain and amplification used the same way I have used them here. "Assuming an ideal (zero output impedance) ampli..." It appears you don't understand how op-amp circuits operate and very little about TIAs. "Current is not amplified by a trans-impedan..." Current is amplified by a TIA, but the output is a voltage. The gain has units of Ohms. Since you can't comprehend this concept I suggest that you don't try editing electronics pages. [[User:Zen-in|Zen-in]] ([[User talk:Zen-in|talk]]) |
Revision as of 03:57, 11 July 2014
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Hi, I don't understand the use of the original research or unverified claims tag here. This is everyday electronic engineering stuff that has been very well presented. Sfrahm 11:10, 26 October 2007 (UTC)
Good article. I hope you wont mind me trying to improve it by Wikifying and generally tidying it!--Light current 00:33, 11 August 2006 (UTC)
- Hi Light current! Thank you for the willingness of cooperation. I had just begun thinking about your last discussions on the page of negative resistance when I noted your changes in the page of transimpedance amplifier.
- Of course, my insertions need improving by a native English speaker(s). I have realized that I have only roughly exposed the topic. I promise you that I will assist you (in return for your editorial help), if you ever decide to join the BG Wikipedia :) Circuit-fantasist 08:06, 12 August 2006 (UTC)
Diagrams
I know it's a pain, but the word 'harmful' in your diagrams gives the wrong impression to readers. Maybe you could change it to 'unwanted' 8-)--Light current 01:06, 11 August 2006 (UTC)
Impede, embarrass, hamper, enervate, decrease, diminish...
I would like to say that something is bad as it impedes, embarrasses, hampers, enervates the excitation input voltage when it strives to create a current. Also, I would like to say that the "bad thing" decreases, diminishes the effective (actual) current-creating voltage VRi = VIN - VR (in this arrangement, the resistor Ri actually acts as a voltage-to-current converter).
- 'Acts in opposition to'; or 'opposes'.
- The "bad thing" REDUCES (or diminishes or cancels) the current-creating voltage VRi = VIN - VR --Light current 20:01, 20 August 2006 (UTC)
"...effectively modifies the excitation voltage VIN..."
According to the considerations abov, we have to write, "...effectively modifies the actual current-creating voltage VRi..." By the way, can you "unearth" some simpler single word (like decrease, diminish etc.) instead the combination "effectively modify"?
What is 'harmful' - resistance, voltage or the both?
- Only, beginning to think about your word substitutions (I agree them) I have gradually realized that actually only the resistance is the "bad thing" in this arrangement (discuss). The voltage drop VR is not a 'harmful' quantity; instead, it is a useful quantity as it is created by the input voltage source, in order to overcome the resistance! In other words, the voltage drop VR is the reaction of the excitation source to the impeding resistance; it is its voltage, not resistance's voltage! So, if you allow me, I will apply the adjective 'undesired' only to the resistance R.
- Maybe, this discussion is also suitable for Ohm's law where it is more precisely to say, "...the voltage source develops a voltage drop across the terminal conductors of the resistors..." instead, "...resistors develop a voltage across their terminal conductors..."
The basic idea behind the passive current-to-voltage converter
I have inserted a para about the basic (non-electrical) idea of the passive version (similarly the active version). The idea is simple and well-known from our life: the impidements cause a pressure; so, in order to create a pressure, an impediment has to be applied.
A new page about the passive current-to-voltage converter?
I suppose to open a new page about passive current-to-voltage converter; IMO, it deserves attention. Then, we may remove the part about the passive version from this page to the new one.
Swapping Transimpedance amplifier and Current-to-voltage converter?
I would like to come up for discussion the title. Actually, transimpedance amplifier and current-to-voltage converter are the same device. Only, I don't know why the first name is more frequently used although
- transimpedance amplifier is more meaningless than current-to-voltage converter
- current-to-voltage converter is more general than transimpedance amplifier as there are two versions (passive and active one) for it.
So, I suggest to make 'Current-to-voltage converter' main page and 'Transimpedance amplifier' - redirected page. Circuit-fantasist 14:47, 12 August 2006 (UTC)
Actually, I would suggest going with the one that is more frequently used which is transimpedance. Also, to say that transimpedance is more meaningless would show a lack of understanding of an transimpedance amplifier. The gain of a transimpedance amplifier is ohms. Hence the name transimpedance. I can't tell if the trans is like transconductance in which that article says it stands for transfer but the same concept. Transconductance means the gain is going to be in Siemens. 155.33.109.148 22:47, 11 August 2007 (UTC)
- I would like to say that the word transimpedance amplifier is more meaningless than the word current-to-voltage converter. Circuit-fantasist 16:06, 14 August 2007 (UTC)
Cleanup
I added the cleanup tag because of formatting and layout. It's rather choppy with very short paragraphs each with a heading. (Information looks good during a cursory look but the layout just makes it hard to follow). RJFJR 21:07, 21 September 2006 (UTC)
- Is it OK enough already? Circuit-fantasist 10:23, 22 September 2006 (UTC)
Transimpedance Amplifier vs. Current to Voltage Converter
A C2VA is not always a TIA but a TIA is always a C2VA. Example: A resistor converts current to voltage, but its not a TIA. The TIA is an idealized model, just like the voltage opamp is an idealized model for simplified calculations. Steve110 20:31, 28 March 2007 (UTC)
- Current-to-voltage converter is the most general term including both the passive current-to-voltage converter (a bare resistor) and active current-to-voltage converter (transimpedance amplifier). There is a close interrelation between the two versions - the active version is come from the passive one; the more complex active version consists of a passive version and a compensating op-amp. The passive version is reversible (it may act as the reverse voltage-to-current converter); the active version is not reversible. Current-to-voltage converter is more natural, clear and meaningful word than transimpedance maplifier. Really, the transimpedance amplifier is an idealized model but the circuit showed on the right is one of the possible practical circuit implementations (maybe, the most popular one). Circuit-fantasist 17:04, 29 March 2007 (UTC)
I have swapped the two pages as the current-to-voltage converter name is more general than transimpedance amplifier one. Now, Current-to-voltage converter begins with the passive version and ends with the active one (see also Voltage-to-current converter).
I have moved also the discussion from this page to Current-to-voltage converter talk page.
Circuit-fantasist 12:06, 17 March 2007 (UTC)
I removed the redirection to Voltage-to-current converter and copied the most recent edits. Zen-in (talk) 02:50, 1 December 2013 (UTC)
Confusing pictures
The pictures in this article have so many layers of annotation in multiple colors that they are extremely confusing. They look like the end result of a lecture, rather than an illustration for an article in an encyclopedia. A simpler set of schematics would be a valuable replacement. Kevin k (talk) 17:08, 11 December 2012 (UTC)
Agreed. The pictures are of low quality, they are too verbose and they don't clearly explain the matter at hand. If someone can simplify the article & pictures - please do it!
Vaxquis (talk) 21:04, 17 September 2013 (UTC)
+1 I am also in agreement. This definitely looks like this is notes from a lecture instead of an encyclopedia page. Reportingsjr (talk) 18:40, 20 October 2013 (UTC)
Page re-write and rename as Transimpedance Amplifier (TIA)
I propose this page get a complete re-write and be renamed Transimpedance Amplifier. In Robert Pease's article he states "we used to call this a current-to-voltage converter,". The technical details on this page are weak and not well presented, despite the excessive verbosity and colorful plots. There is no discussion of compensation or the gain/BW tradeoff. Zen-in (talk) 16:49, 2 November 2013 (UTC)
- I agree with the name change. "Current-to-voltage converter" should redirect to newly named page.Constant314 (talk) 14:52, 22 November 2013 (UTC)
- Both Transimpedance Amplifier (TIA) and Transimpedance Amplifier are non-conforming names. Transimpedance amplifier is ok though. SpinningSpark 16:40, 22 November 2013 (UTC)
- I moved the most recent version of this pages content (after removing CD's well-intentioned graphi-analytic discussion). What should we do with this page now? Maybe describe transistor and other simple current to voltage circuits? Or is that too trivial? Zen-in (talk) 02:56, 1 December 2013 (UTC)
- Oops, I remember a discussion about forks a while back so I replaced the content of this page with a redirect to Transimpedance amplifier. Anyone object? Zen-in (talk) 03:09, 1 December 2013 (UTC)
- You have also forgotten that cut and paste moves are not desirable for licencing reasons. I have deleted the forked transimpedance amplifier and reverted the redirect. Please move the article using the move button (if you still desire to do so) and also move this talk page. I will restore your most recent edits once you have done that (as long as there are no intervening edits while the page is still here). Next time you should request deletion of the target page by an admin if the wikimedia system stops you from moving via the move button. SpinningSpark 09:50, 1 December 2013 (UTC)
- Yes, I guess I'm not the only one who is out of practice. I hope this page is more useful now. I will try to make the technical parts more descriptive. Transimpedance amplifiers are somewhat complicated beasts so simplifying the analysis would not be useful to anyone. A section showing why transimpedance amplifiers tend to oscillate and have gain peaking will be added. Zen-in (talk) 18:20, 1 December 2013 (UTC)
- I have now restored your deleted edits as promised, but since the article has been edited in the intervening time, they are no longer in the current article. You can retrieve them from the history if you so wish. SpinningSpark 18:51, 1 December 2013 (UTC)
- That's ok. I added the deleted edits and then some. The current version has more corrections. Zen-in (talk) 21:52, 1 December 2013 (UTC)
- Yes, I guess I'm not the only one who is out of practice. I hope this page is more useful now. I will try to make the technical parts more descriptive. Transimpedance amplifiers are somewhat complicated beasts so simplifying the analysis would not be useful to anyone. A section showing why transimpedance amplifiers tend to oscillate and have gain peaking will be added. Zen-in (talk) 18:20, 1 December 2013 (UTC)
- You have also forgotten that cut and paste moves are not desirable for licencing reasons. I have deleted the forked transimpedance amplifier and reverted the redirect. Please move the article using the move button (if you still desire to do so) and also move this talk page. I will restore your most recent edits once you have done that (as long as there are no intervening edits while the page is still here). Next time you should request deletion of the target page by an admin if the wikimedia system stops you from moving via the move button. SpinningSpark 09:50, 1 December 2013 (UTC)
- Oops, I remember a discussion about forks a while back so I replaced the content of this page with a redirect to Transimpedance amplifier. Anyone object? Zen-in (talk) 03:09, 1 December 2013 (UTC)
Overly general statements in Bandwidth and stability section
You are doing a great job. Consider this as a minor suggestion. I think a couple of your sentences are overly broad. First, “There is no cut and dry formula for calculating the capacitor value that works for all cases”. If all cases includes all types of amplifiers, loads, sources, applications, stability and bandwidth requirements then the statement is trivially true and applies to all amplifier design. Second “the iterative method required to optimize the value”. An iterative method can be used but there are many cases where those sufficiently skilled in algebra do not need to iterate. I have not looked at St Bob’s article, but I suspect he formed his opinions in the bad old days when opamps would go crazy with even a slight capacitive load and the spec sheet didn’t mention it. You were pretty much stuck with iterating the hardware (soldering real capacitors onto the breadboard to see what would happen). But in the modern era, opamp designers have recognized that there is often some capacitance hanging on the output. They have built in some tolerance to capacitive loads and they even spec it. If the series combination of Ci and Cf is less than the opamp’s specified capacitance driving capability then you can probably optimize the design on paper. I suppose you might iterate the paper design. Maybe that is what you meant. Still, I would replace “required” with something less compelling.Constant314 (talk) 05:18, 5 December 2013 (UTC)
- Thanks for the support and compliments. The last few sentences need some work. I have slowed down in the last couple of days since I'm very busy with other things on weekdays. I will be adding something about the bandwidth and will try to re-word that last section. Graeme's analysis of tia instability and their compensation are very well presented. I have just skimmed over his analysis here and recommend others read his book for the full story. My limited experience designing and optimizing tias, for quantum dot sensors, has taught me iteration is needed and any textbook calculation of Cf just keeps you on the fairway. There are no hole in ones in this game. The gain-setting resistor and even the kind of load the tia is driving affect the final value. Even the placement of the cap makes a big difference. While this gets beyond what an encyclopedia should present, it would be incorrect to write that a paper design can be iterated or will ever be optimal. Zen-in (talk) 15:11, 5 December 2013 (UTC)
- I’ve done it twice. Depending on what you mean by iterating, I may have iterated the paper design but not the hardware. I suppose it was optimal in the sense that it was not noisier than the paper analysis said it would be.Constant314 (talk) 04:17, 6 December 2013 (UTC)
- Yes I guess you can design it on paper and it won't oscillate after the solder has frozen. I think providing links to something St. Robert wrote or other sources is sufficient. The level of detail required to describe the design and iteration of compensation may not belong here and could just disappear even quicker. There are a lot of other aspects to tias that should be covered. If you have the time to add something about the bandwidth of tias go for it. I have left that part out for now. Maybe it should be covered on the opamp page but if it is well done it will likely get moved and live on somewhere else. Zen-in (talk) 07:20, 6 December 2013 (UTC)
- I'll just add the word often in front of required.Constant314 (talk) 22:48, 6 December 2013 (UTC)
- Yes I guess you can design it on paper and it won't oscillate after the solder has frozen. I think providing links to something St. Robert wrote or other sources is sufficient. The level of detail required to describe the design and iteration of compensation may not belong here and could just disappear even quicker. There are a lot of other aspects to tias that should be covered. If you have the time to add something about the bandwidth of tias go for it. I have left that part out for now. Maybe it should be covered on the opamp page but if it is well done it will likely get moved and live on somewhere else. Zen-in (talk) 07:20, 6 December 2013 (UTC)
- I’ve done it twice. Depending on what you mean by iterating, I may have iterated the paper design but not the hardware. I suppose it was optimal in the sense that it was not noisier than the paper analysis said it would be.Constant314 (talk) 04:17, 6 December 2013 (UTC)
Transimpedance amplifier gain
Copied from User talk:Constant314
- I reverted the first section back to a discussion about amplification and gain since it was starting to get muddled. Gain, as described in a Wikipedia page is not tied to any units. The gain, or amplification of a TIA is measured in Ohms. I don't believe there is any ambiguity in stating the current is amplified anymore than it would to say what comes before a speaker is an amplifier. Zen-in (talk) 05:53, 10 July 2014 (UTC)
- They are called trans-impedance amplifiers because their gain is an impedance. The input is current and the output is a voltage. The only gain that you can multiple a current by and get a voltage has the units of impedance or ohms. In fact, the gain of the circuit in the first picture is RF. Assuming an ideal (zero output impedance) amplifier, the output current depends on the amplifier load and can range from zero to arbitrarily large. Current is not amplified by a trans-impedance amplifier. For that you would need a current amplifier.Constant314 (talk) 21:08, 10 July 2014 (UTC)
- And by the way, Wikipedia pages are not considered reliable sources.Constant314 (talk) 21:09, 10 July 2014 (UTC)
- No you are wrong about this. Amplification does not require the same units at the input and output. There is no ambiguity in how this is stated in the article. Gain is an important property of TIAs and it is always stated in Ohms. Open any good book on electronics, like the ones I consulted in writing this page, and you will see the terms gain and amplification used the same way I have used them here. "Assuming an ideal (zero output impedance) ampli..." It appears you don't understand how op-amp circuits operate and very little about TIAs. "Current is not amplified by a trans-impedan..." Current is amplified by a TIA, but the output is a voltage. The gain has units of Ohms. Since you can't comprehend this concept I suggest that you don't try editing electronics pages. Zen-in (talk)