total rail current can be read by placing the cursor over the voltage source. when you see a current probe symbol, click on it. or you can measure the device current in the same way. hold the cursor over the collector pin (or emitter, or emitter resistor) and click when you see the current probe symbol. the voltage probe is pointy, the current probe is a loop. this is, of course AFTER you have run a sim of the circuit. the emitter current will be a bit different than the collector current, because it will be the sum of the collector current and the base current.
you may want to run a sim with no signal if you just want to check the idle current. also be aware, that since it IS a sim, you can run ANY transistor far beyond it's rated current without any indication of a problem (it's interesting to see a 2N2222 running at 20A collector current with no ill effects
).
you may want to run a sim with no signal if you just want to check the idle current. also be aware, that since it IS a sim, you can run ANY transistor far beyond it's rated current without any indication of a problem (it's interesting to see a 2N2222 running at 20A collector current with no ill effects
).
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You can also insert a voltage source into a net as a current probe. Set the DC voltage=0, then measure the current as explained by uncleje613 above. This is rarely needed, but handy where you want to see the total current going into multiple devices, for example looking at the total rail current for the front end of an amp separate from the rail current for the output stage.
keantoken and mightydub,
On "Common Issues ...." it says:" LTSpice uses perfect resistors, capacitors and inductors by default," Actually, by default, inductors include a .001 ohm resistor. You can change it to whatever you want by right clicking on the component and inserting what you want in the box.
Rick
On "Common Issues ...." it says:" LTSpice uses perfect resistors, capacitors and inductors by default," Actually, by default, inductors include a .001 ohm resistor. You can change it to whatever you want by right clicking on the component and inserting what you want in the box.
Rick
Hi everyone, I just thought I'd echo this post from the LTSpice yahoo group.
It sounds like a rant, but give it due process. There are multiple people with this opinion, and it's more or less the basis of this project.
My observation is that the help file isn't that great really, it never helped me get subcircuits working.
A little more context:
I don't want to argue over the points made in this writing, that's been done enough on the LTSpice group. Rather, I want to consider the concerns of our audience.
I think we should at least mention that many (most?) new users find the help file useless or even frustrating. The Wiki is a help file too, so I think it's fair to suggest that they might find the answers to their questions faster by going through the wiki (I found it very time consuming to try and sift through the help file, which isn't even that large).
Personally, I began using LTSpice with absolutely no working knowledge of electronics. I learned most of what I know through LTSpice, and so I can see why a beginners' guide would certainly be helpful to students of electronics. I don't believe that only experienced people should use it, because it's a great resource for both students and engineers.
- keantoken
It sounds like a rant, but give it due process. There are multiple people with this opinion, and it's more or less the basis of this project.
My observation is that the help file isn't that great really, it never helped me get subcircuits working.
A little more context:
I don't want to argue over the points made in this writing, that's been done enough on the LTSpice group. Rather, I want to consider the concerns of our audience.
I think we should at least mention that many (most?) new users find the help file useless or even frustrating. The Wiki is a help file too, so I think it's fair to suggest that they might find the answers to their questions faster by going through the wiki (I found it very time consuming to try and sift through the help file, which isn't even that large).
Personally, I began using LTSpice with absolutely no working knowledge of electronics. I learned most of what I know through LTSpice, and so I can see why a beginners' guide would certainly be helpful to students of electronics. I don't believe that only experienced people should use it, because it's a great resource for both students and engineers.
- keantoken
Interesting.
Ironic that this comes from the Yahoo LTspice group (of which I am a member) where many of the responses are along the lines of "if you'd look at the help file..."
As someone who has picked up LTspice, Eagle PCB, and Speaker Workshop (now there's a tough learning curve, and a minimalist help file) I have a different perspective. Maybe it is a generational thing, or just a philosophical difference, but when my kids ask me "Daddy, how do I spell (insert random word here)" my response is "how do you think it is spelled?" Then they give it a try, and if they get it right, they get the sense of accomplishment and confidence that they figured it out for themselves. And if they get it wrong, I can ask questions like "what's the rule about i before e?" and help them learn something that they can apply next time. So someone who goes off on a rant when it is suggested that they RTFM sounds like a spoiled brat to me. Sorry, Charlie. There's lots of learning, and satisfaction, in figuring out problems yourself.
You don't have to look very far back in the posts to find a perfect example of the sort of question that a new user could have easily answered by opening Help and reading a little bit about the waveform display.
Really, the help file has almost everything you need, though sometimes you have to dig a little bit. I find that in the process of digging for the answer I often come across some nugget to remember for later.
But hey, it's a wiki. I can edit it. Any of you DIYaudio members can edit it, and you SHOULD do so, if you can IMPROVE it. If there's information that is missing, ADD it! Other people have contributed their time and knowledge to putting the information out there. Those who are offended at one line of text (yes I'm the author) that suggests they try to figure out the answer for themselves are welcome to put their energy into improving and expanding the wiki.
Ironic that this comes from the Yahoo LTspice group (of which I am a member) where many of the responses are along the lines of "if you'd look at the help file..."
As someone who has picked up LTspice, Eagle PCB, and Speaker Workshop (now there's a tough learning curve, and a minimalist help file) I have a different perspective. Maybe it is a generational thing, or just a philosophical difference, but when my kids ask me "Daddy, how do I spell (insert random word here)" my response is "how do you think it is spelled?" Then they give it a try, and if they get it right, they get the sense of accomplishment and confidence that they figured it out for themselves. And if they get it wrong, I can ask questions like "what's the rule about i before e?" and help them learn something that they can apply next time. So someone who goes off on a rant when it is suggested that they RTFM sounds like a spoiled brat to me. Sorry, Charlie. There's lots of learning, and satisfaction, in figuring out problems yourself.
You don't have to look very far back in the posts to find a perfect example of the sort of question that a new user could have easily answered by opening Help and reading a little bit about the waveform display.
Really, the help file has almost everything you need, though sometimes you have to dig a little bit. I find that in the process of digging for the answer I often come across some nugget to remember for later.
But hey, it's a wiki. I can edit it. Any of you DIYaudio members can edit it, and you SHOULD do so, if you can IMPROVE it. If there's information that is missing, ADD it! Other people have contributed their time and knowledge to putting the information out there. Those who are offended at one line of text (yes I'm the author) that suggests they try to figure out the answer for themselves are welcome to put their energy into improving and expanding the wiki.
i agree, the help file isn't helpful like it should be and i don't use it much unless i want to find out how to use a certain command or spice directive.... and i'm an engineer.....
there are things that LTSpice does and error messages that aren't mentioned at all in the help file. i had to do a lot of digging and searching on the yahoo group to find out what DEFCON 1 was. i found the "help" on using and creating subcircuits and symbols to be too vague to be of any use. much of the help file seems to assume you already know SPICE. but when i went to school, SPICE, if it existed at the time , was not taught. i think there should actually be 2 other levels of help file included, one for beginners (and maybe a linked tutorial), and one for troubleshooting LTSpice problems (and possibly a linked tutorial for it, which teaches what all of the control panel settings do). quite often i will ask about why something doesn't seem to work, and get the answer "did you try the alternate solver?". of course i didn't try the alternate solver because i don't know what it does differently from the normal solver.... i just checked, and it seems there's a short blurb about the alternate solver. but the little blurb doesn't help me figure out when it is a good time to try the alternate solver.
there is also a "getting started" guide that cover most of the basics. LT added it in 2008. it looks like a pdf version of a power point slide show, and it has a lot of stuff in it that would have definitely improved my learning curve.
there are things that LTSpice does and error messages that aren't mentioned at all in the help file. i had to do a lot of digging and searching on the yahoo group to find out what DEFCON 1 was. i found the "help" on using and creating subcircuits and symbols to be too vague to be of any use. much of the help file seems to assume you already know SPICE. but when i went to school, SPICE, if it existed at the time , was not taught. i think there should actually be 2 other levels of help file included, one for beginners (and maybe a linked tutorial), and one for troubleshooting LTSpice problems (and possibly a linked tutorial for it, which teaches what all of the control panel settings do). quite often i will ask about why something doesn't seem to work, and get the answer "did you try the alternate solver?". of course i didn't try the alternate solver because i don't know what it does differently from the normal solver.... i just checked, and it seems there's a short blurb about the alternate solver. but the little blurb doesn't help me figure out when it is a good time to try the alternate solver.
there is also a "getting started" guide that cover most of the basics. LT added it in 2008. it looks like a pdf version of a power point slide show, and it has a lot of stuff in it that would have definitely improved my learning curve.
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Spice wasn't written for beginners. There are entire college level courses that teach spice. If you can't explain the difference between voltage and current, write out Ohm's law and the equations that describe the relationships between voltage and current for capacitors and inductors, or describe the differences between common-base and common-emitter transistor configurations, then step away from the simulator and pick up a basic text book on electrical engineering. Spice isn't going to teach you EE, it's a glorified calculator that assumes you already know at least the basics.
The LTspice Help is just that - help for LTspice the tool, not an all purpose reference course in electrical engineering. Take the time to learn the tool, figure out how to read a spice netlist and draw the circuit diagram that it represents.
Patience, Grasshopper. Understanding takes time. Enlightenment takes longer.
You started this whole thing - you'd better contribute!
I really hope to see many people conribute to this as I'm sure there's a lot that I can still learn.To anyone thinking of joining the fun, if you're hesitant because you haven't touched a wiki before, please, just jump in. Click the EDIT tab and look at the formatting options. Hit the Preview button to see what effect changes have. If you don't want to change anything, then just don't click Save Changes, use the Back button on your browser and you won't get into trouble. If you do mess it up, it is easy to revert to an earlier version.
the yahoo LTSpice group has several tutorials in their files section. there are also some interesting models there for complex functions of simple devices such as behavioral models of incandescent bulbs, neon lamps, and spark gaps. for such simple devices as these, there are a lot of things happening when they are operating...
Well, nothing on modeling but I've just revived the DIY Guides section from the old wiki, where I contributed several pages.
http://www.diyaudio.com/wiki/DIY_Guides
- keantoken
http://www.diyaudio.com/wiki/DIY_Guides
- keantoken
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also be aware, that since it IS a sim, you can run ANY transistor far beyond it's rated current without any indication of a problem (it's interesting to see a 2N2222 running at 20A collector current with no ill effects
This was a conscious/deliberate FEATURE put in by the guy who wrote LTSpice. The reasoning behind this feature is that if the simulation should error out when any parameter fails, you lose information. Whereas if the simulation continues even after parameters are exceeded, then you can extract a lot of useful information from it.
e.g. in your case, the simulation tells you that you need a 20A transistor, which you wouldn't have known if the simulation just errored out saying max collector current exceeded.
There are other spice simulators that error out the way you want.
i understand that.... it would be nice to have a feature that could be toggled to indicate a problem during a sim. i think a while back on the LTSpice group i suggested an animation of a component "letting the smoke out".... i think there is an indication (only when running SMPS simulations with LTC IC's) that devices have gone beyond their ratings. they might have removed that feature since the last time i saw it in operation.
i think there is an indication (only when running SMPS simulations with LTC IC's) that devices have gone beyond their ratings. they might have removed that feature since the last time i saw it in operation.
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inverse RIAA, ckt below. use the values in parenthesis for the most accurate curve. input the signal source on the left, no series resistance for the signal source is required. in LTSpice remember to use MEG instead of M, so the 1M59 will become 1.59MEG if you use the default op amp, set the GBW to 10Mhz
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