I've attached the LTSpice simulations
Sorry, not visible.
Yes.You can change the extension to.TXT and upload the files.
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You can change the extension to.TXT and upload the files.
Please don't forget to include any models which are not included on the LTSPICE software itself.
Here's an update to the circuit.
I added the model for the LT6654 and changed the diode to a 1N4148.
I also added R2, R3, and C3 to compensate the op amp response and minimize the overshoot in the current output waveform.
It now seems to take about 10ms to settle after power-on.
View attachment 131823
Here's an update to the circuit.
I added the model for the LT6654 and changed the diode to a 1N4148.
I also added R2, R3, and C3 to compensate the op amp response and minimize the overshoot in the current output waveform.
It now seems to take about 10ms to settle after power-on.
View attachment 131823
Actually it's overshoot since it goes to a larger magnitude than the flat portion of the waveform.......................
This is interesting. I updated my circuit to match yours but I'm still getting a pretty significant undershoot compared to your results.
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Actually it's overshoot since it goes to a larger magnitude than the flat portion of the waveform.
(If you reverse the direction of Rload in the circuit you will see a positive going current, as I have in my sim.)
But it is curious that you simulation is different from mine.
Offhand I see no difference between the two circuits.
Upload your .asc file and I'll run it to see if I can duplicate the waveform.
I simulated your circuit from post #12 without any changes, in my LTSpice IV and it showed no significant overshoot (see below).
(I did rename it circuit2a to differentiate if from the original).
It's a total puzzle to me why there would be a difference between your sim and mine.
You didn't make any changes to the default Spice settings in the Tools/Control Panel, did you?
View attachment 131832
A better designed loop powered circuit would measure the total loop current, e.g. by a shunt resistor in the negative line.
No.@crutschow
Your simulation is different due to the start time.
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Does this matter?
Your comment about current deviations made me think that you want exactly defined loop currents, as usual in 4-20 mA circuit. But after reviewing your posts I'm not sure if it's an actual problem that variation of voltage regulator quiescent current is reflected in the loop current.
Similarly, I don't understand what's your specific problem with getting a 7 µs low pass filtered current (by the working of C1) instead of sharp square wave. If you connect a long cable with the some capacitance, the waveform rise time will be affected anyway.
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