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What do you mean by "not working any more"?
Your circuit operates as a voltage follower, quite complicated at it.

Many thanks for help
/g/LTspice/files/Temp/vround_issue
Best

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We can't help much unless you let us see more of what you are doing. Upload your .ASC file AND all the other files required to run the simulation, but not .RAW? and .LOG files or pictures,? in a ZIP archive to Files => Temp.

Go to the web page: /g/LTspice/topics. Click on Files in the list on the left. Then click on Temp. Then click on New Upload in the blue box at top left. Click on Upload File in the drop-down menu. Then send a message to tell us that you did that.

Dear,

?am a beginner? in LTSpice. I have an issue with Virtual ground and amplifying a signal. I am amplifying a 10mV signal that wors well.?

When i replace the power suppliers by a DC circuit, a splitter and a virtual ground, this is not working anymore.? ??

?

I guiess it is probably related to a virtual ground issue with LTspice but cannot fing online any solution.

Many thanks for help.

Bertrand?

Dear,

?am a beginner? in LTSpice. I have an issue with Virtual ground and amplifying a signal. I am amplifying a 10mV signal that wors well.?

When i replace the power suppliers by a DC circuit, a splitter and a virtual ground, this is not working anymore.? ??

?

I guiess it is probably related to a virtual ground issue with LTspice but cannot fing online any solution.

Many thanks for help.

Bertrand?

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I agree that setting R4 value to zero should raise a flag.

But the underlying netlist hasn't changed. Why didn't it renumber the nodes when R4 was silently discarded (without telling the user - there's nothing in the log file stating what has been done)?

To be honest, I hadn't realised that setting R4's value to zero would be permitted. I had expected there to be a message in the log file saying "Fatal Error: r4: Resistance must not be zero", because I knew from experience that's what you get if you assign the value of R4 to zero using a .param directive. Having found that it was accepted, I dug a little further.

Regards,
Tony

On 30/05/2024 11:02, John Woodgate wrote:

I think that LTspice just puts up a simple flag 'schematic changed', so it looks at the new schematic as a completely new one, and it numbers the nodes consecutively from 1 upwards

On 2024-05-30 09:51, Tony Casey wrote:

LTspice has already "silently" removed it. Having done that, why does it then renumber node N004 to N003, when R4 is removed from the schematic?

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But the underlying netlist hasn't changed. Why didn't it renumber the nodes when R4 was silently discarded (without telling the user - there's nothing in the log file stating what has been done)?

To be honest, I hadn't realised that setting R4's value to zero would be permitted. I had expected there to be a message in the log file saying "Fatal Error: r4: Resistance must not be zero", because I knew from experience that's what you get if you assign the value of R4 to zero using a .param directive. Having found that it was accepted, I dug a little further.

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I think that LTspice just puts up a simple flag 'schematic changed', so it looks at the new schematic as a completely new one, and it numbers the nodes consecutively from 1 upwards

LTspice has already "silently" removed it. Having done that, why does it then renumber node N004 to N003, when R4 is removed from the schematic?

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On 30/05/2024 04:22, zkf0100007@... wrote:

A simple J310 amlifier.
When I added R4, even the value is 0R, ?the output voltage on R3 is 50mvpp.
When I removed R4, the output voltage on R3 is only 5mvpp, same as the input voltage.
It is strange.
Could anyone tell me why?

The explanation has already been noted.

But did anyone look at the netlist of the original circuit with R4? It's not there! Hovering the mouse over either end of R4 shows that both ends are node N001. LTspice has already "silently" removed it. Having done that, why does it then renumber node N004 to N003, when R4 is removed from the schematic?

The details are interesting. In the first case, the netlist doesn't have a node N002. It's clear that this would have been the node name at the right end of R4 if it's value wasn't 0. But having removed it from the netlist, both ends of R4 have become node N001, but the rest of the netlist is left as-is without N002. When R4 is physically removed from the schematic, all other lines apart from those for V2 and C3 are renumbered, even though there was actually no change to the circuit connectivity.

J1 N003 N006 N007 J310??? ??? ??? ? ?? J1 N002 N005 N006 J310
R1 N006 0 470K??? ??? ??? ??? ??? ? ?? R1 N005 0 470K
C1 N006 N005 220p??? ??? ??? ???? ? ?? C1 N005 N004 220p
V1 N005 0 SINE(0 5m 7meg) AC 2??? ? ?? V1 N004 0 SINE(0 5m 7meg) AC 2
L1 N001 N003 100? Rser=1m??? ???? ? ?? L1 N001 N002 100? Rser=1m
R2 N007 0 160??? ??? ??? ??? ???? ? ?? R2 N006 0 160
C2 N007 0 0.1???? ??? ??? ??? ??? ? ?? C2 N006 0 0.1?
C3 N001 0 0.1???? ??? ??? ??? ??? ?? ? C3 N001 0 0.1?
V2 N001 0 12??? ??? ??? ??? ??? ? ? ?? V2 N001 0 12
C4 N004 N003 0.01???? ??? ??? ??? ? ?? C4 N003 N002 0.01?
R3 N004 0 1K??? ??? ??? ??? ??? ? ? ?? R3 N003 0 1K

--
Regards,
Tony

At 07:27 PM 2024-05-29, you wrote:

Greetings everyone, I need a 741 model or it could be another op amp that has offset correction pins, the need for these pins is because I'm making some circuits for teaching purposes, such as the full wave rectifier precision, these circuits are didactic and reinforcement in nature.

grateful
--
Carlos Delfino
Quem sou:?
Keybase (PGP):
ORCID:?

You can just add the two pins to a transistor-level model of the LM741.

If you can't find a decent transistor-level SPICE model, Sedra/Smith has one in Chapter 10 of?
SPICE for for Microelectronic circuits, 3rd edition

You would connect the tops of the two 1k resistors R1 and R2 in Fig. 10.1

As others have said, using the offset null pins tends to introduce excessive temperature dependence.

Best regards,
Spehro Pefhany

Roy wrote, "... I would suggest that you not teach it, because it was?a bad idea that did not catch on."

Then it might be useful for teaching an example of inferior circuit design, something that is usually best not done.

The other thing to remember is that "all" simulations with 741 op-amps are ideal and likely have zero (or nearly zero) input offset voltage.? The transistor matching in the SPICE model is perfect.

Andy

I mean that remove R4, and connect with a wire.

Thank you very much!
?
I deleted V(N004) from the plots and click that node to plot it again, the output on R3 is still 100mvpp.

Small typo correction.? I wrote: "Any name given a nodename stays put."? That should be "Any net or node given a nodename stays put" or does not change.

Andy

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It is not strange.
If you remove R4, you disconnect the power rail from the active stage, which then does not work as expected.

zkf0100007, I see your uploaded file now.? Thank you.

When run as is, with R4 = 0, the output voltage across R3 is approx. 100 mVp-p.? Not 50 mV pp, but I understand that was probably what you really meant.

When R4 is simply removed, there is nearly no output across R3, but I'm sure that is not what you meant

When R4 is removed and replaced by a wire, the output voltage across R3 is still 100 mVpp.? It did not change.

HOWEVER, if you are still plotting V(N004), note that N004 is not the same circuit node anymore!? By removing R4 and replacing it by a wire, you have eliminated one unnamed node.? Because all of the nodes in your circuit (except for Ground) are not named, LTspice re-orders the unnamed nodenames so that they are sequential.? The result is that the top of R3 is now N003 instead of N004.? By plotting V(N004), you are looking at the input signal, not the output signal.

Two remedies:? Either delete V(N004) from the plots and click that node to plot it again, or - even better - add Labels (nodenames) to your circuit.? Any name node given a nodename stays put (does not change).? Any node without a name can and will change its name.? Avoid that by adding your own nodenames.

Andy

I have uploaded the file named ‘J310_AMP.asc??’
Thanks!

zkf0100007 wrote, "A simple J310 amlifier."

Where is it?? We can't read your mind.? Please, if you have a schematic, upload the schematic (.asc) file, plus any SPICE models that did not come with LTspice.? No pictures, please.? Upload to the Temp folder, by first navigating to Files > Temp, and then click the "New/Upload" button.

Then come back here and send a reply, telling us the file that you uploaded.

Andy