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Re: Is the Group down?
Same for me. I see some note while waiting about "waiting for proxy." --s.a.hill (new to group) On Thu, May 29, 2014 at 3:12 PM, Vlad imbvlad@... [LTspice] <LTspice@...> wrote:
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Is the Group down?
Hello
I keep getting errors whenever I try to access the web page of the Group, no matter if it's the files or the conversations, but I seem to be able to post replies from within GMail. Is this a general (hopefully temporary) flaw? Vlad ______________________ ltspicegoodies.ltwiki.org -- holding, among others: a universal analog/digital filter, block-level models for power electronics (and not only), math blocks with a more stream-lined approach, some digital ADC, DAC, (synchronous-)counter, JKflop, etc. |
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Re: Clipping a Universal op-amp
On a second thought, the "sw" only might do (it has "vt" and "vh"),
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but if an additional delay is needed (to avoid "time step too small: errors), the comparator will come in handy. Vlad ______________________ ltspicegoodies.ltwiki.org -- holding, among others: a universal analog/digital filter, block-level models for power electronics (and not only), math blocks with a more stream-lined approach, some digital ADC, DAC, (synchronous-)counter, JKflop, etc. I don't really understand your purpose but, given what you have said:OK: Now can I rig a feedback which essentially lies dormant until theyou could make use of a comparator (use the Schmitt A-device with "vt=50m |
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Re: Li-ion BAttery models
Thx Woody
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Re: Clipping a Universal op-amp
I don't really understand your purpose but, given what you have said: > OK: Now can I rig a feedback which essentially lies dormant until the > error voltage exceeds maybe 50mV, then jumps in to force balance?
you could make use of a comparator (use the Schmitt A-device with "vt=50m vh=0") and a VCVS (element "sw") with proper Ron/Roff. I'll just leave the "how" and "why" for yourself. Vlad ______________________ -- holding, among others: a universal analog/digital filter, block-level models for power electronics (and not only), math blocks with a more stream-lined approach, some digital ADC, DAC, (synchronous-)counter, JKflop, etc. |
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Re: Clipping a Universal op-amp
Well, suppose you have a gain 2 non-inverting setup. Vin+ > Vdd/2 means the op-amp cannot actually make the summing node Vin- anything like Vin+.
So Vdd=5, Vin+=5, Vin- = B.rail = 2.5: error is +2.5 - not a "working/normal" error voltage but an ERROR voltage (big time). So the output hits the rails. As Vin + gets higher, the error voltage Vin+ - Vin - rises from a normal "enough to drive the loop via AB" to something crazy lit 1, 2 or more volts. OK: Now can I rig a feedback which essentially lies dormant until the error voltage exceeds maybe 50mV, then jumps in to force balance? Yes - the output will not then be 'correct'. But it would be wrong anyway, and I at least the output is not at the rail. |
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Re: Model for H11L1 optocoupler
John Perkins wrote: ? ?"Does anyone know where I can get a model for the H11L1 optocoupler?" There is one in this group, in the Files section. ? ?"There where some messages about this part a few years ago (2011), and it appears that someone came up with a model and posted it, but it is no longer available." I just downloaded it. ?I don't know anything about the H11L1, but the schematic seems appropriate for an opto-coupler. ?Anode, Cathode, Out, Gnd, and Vcc pins. ?It looks like it is meant to be used as a subcircuit, a lower-level hierarchical page. The ZIP file that is in the same directory ("AN3006_60Hz_4.zip") has a slightly different version of the same H11L1 schematic, plus an LTspice symbol
?for it ? that can be used to place it on your schematic for simulation.Regards, Andy |
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Re: Li-ion BAttery models
I need Li-ion battery model that can be simulated in lt-spice (4.2v) rather than charging ckt...If any1 had it..plz post it to me Thanking u On Thursday, May 29, 2014 8:27 PM, "Andy
Andrew.Ingraham@... [LTspice]" wrote:
?
Lohith Vamsee wrote: ? ?"...?I need a li-ion battery model inorder to simulate.
? ? Can u suggest me some links or models?"
There may be a few in our group's Files section. ?Download the Table of Contents file (see instructions on the group's main webpage) and search it for "lithium". ? A few matches come up. ?It's not much, but you might find one of them works.
Regards,
Andy |
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Re: How can I make my simulation oscillate like my poorly designed PC board does?
I really have to bite my tongue here over Carl's poor aim at uploading files.
LTspice should be able to reproduce the transitory MOSFET oscillation just fine as long as the circuit model is reasonably correct.? The rule of thumb for stray inductance is about 10nH per centimeter, so throw out all the strays from your schematic and start over as follows. Add 5nH directly in series with each MOSFET terminal to represent the lead inductance.? Add 100nH in series with the 50 ohm drive to the gate to account for your poor layout.? Add 20nH in series with the 300pF capacitor.? You also could add 5pF to ground from the junction of the 100nH drive and 5nH gate lead inductance. Now you should see the oscillation.? Note that the exact values given above don't matter unless you wish to match exactly the frequency and amplitude of the oscillation.? If this circuit were running from a higher drain voltage, the oscillation would be large enough to rupture the gate and destroy the device (try increasing the power supply to 25 volts and see what happens). The standard cure for this problem is to insert a damping resistance in series with the drain-to-gate capacitor that has a value equal to or somewhat less than the gate drive resistor (20 to 50 ohms in this case). ---In LTspice@..., <Andrew.Ingraham@...> wrote : Carl wrote: ? ?"I've uploaded my circuit (Oscillating Miller FETs.asc) for your viewing pleasure." Unfortunately you uploaded it to the wrong Yahoo Group! Please re-upload it to THIS group, the [LTspice] group. ?The Files area in this group is the right place to put it, in the Temp directory. Regards, Andy |
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Re: cursor dialog in way of schematic
This is the problem
1. Maximise LTSpice 2. Maximise the schematic 3. You run it, add cursors. 4. Swap back to tab: It's a pain to have to close the dialog - and moving it won't always help, as you'l have already placed it where you wanted when looking at the plot. |
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cursor dialog in way of schematic
The cursor dialog shown on plots lives on top of the
schematic too: even in "full-screen" mode (not tiled, not cascaded). Surely it is not a good thing that the cursor dialog is visible when I change tabs in full-screen mode ? (It's fine in Tile or Cascade mode) Yes, sure "I can just delete or move it"... The way I see it, working full-screen (tabs at top) means "I want to see what the tab says over the full application window" not "I want to see all of the schematic and any dialogs associated with the plots". |
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Re: How can I make my simulation oscillate like my poorly designed PC board does?
It can be a real chore to make something oscillate when it doesn't want to. You mentioned a long trace. ?Does your schematic include wires or traces? ?I mean REAL wires? ?SPICE nets are ideal: zero length, zero inductance, zero capacitance, no delay, no coupling ... unless you account for them. ?Another cause for oscillation can be poor grounds, not realizing that "ground" is an artificial and impossible concept. ?Ground potential is not the same everywhere. ?If your layout is sloppy, then there is potential for many "ills" that could be affecting you (grounding, wire lengths, coupling between everything, etc.) that you would need to add to the simulation.
It can take a lot of work to include many of these parasitics. ?It's impossible to include them all.
How good are your FET models? ?Do your transistor models include lead inductances and such? ?If the model is only a .MODEL statement (not a .SUBCKT), then it does not. ?Some VHF/UHF oscillations can be caused by resonance in transistor leads.
You said the oscillation occurs half way up the waveform. ?If this a switching circuit with nominally square wave inputs and outputs, this implies coupling from output into input, which lets it oscillate when the transistor passes through its linear (amplifying) region. I am puzzled by the use of the Miller capacitance to apparently stop the oscillation. ?An oscillation occurs because there is gain, but something has not enough loss (too high Q) to prevent it. ?Adding capacitance moves the frequency but doesn't add loss, so it's probably not the right way to stop an oscillation. ?It just shifts it to a different frequency. ?You might get lucky by shifting it to a frequency that happens to have greater loss or less loop gain, but I think that's taking a chance.
If you haven't done this already, you will want to make sure to use a very small maximum timestep in the .TRAN statement, and probably turn off waveform compression (.options plotwinsize=0), just to make sure the simulation doesn't miss anything.
Regards,
Andy |
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Re: Clipping a Universal op-amp
John Woodgate
In message <lm7khm+a0mhfa@...>, dated Thu, 29 May 2014,
"sineysitch@... [LTspice]" <LTspice@...> writes: Would that actually help with my overdrive (saturation) recovery issue?I'm sorry, but I can't understand what you want to do. It seems self-contradictory. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: How can I make my simulation oscillate like my poorly designed PC board does?
Carl wrote:
? ?"I've uploaded my circuit (Oscillating Miller FETs.asc) for your viewing pleasure." Unfortunately you uploaded it to the wrong Yahoo Group! Please re-upload it to THIS group, the [LTspice] group. ?The Files area in this group is the right place to put it, in the Temp directory.
Regards,
Andy |
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Re: Clipping a Universal op-amp
Hi John,
Would that actually help with my overdrive (saturation) recovery issue? That is, I'd like to be sure the op-amp itself never hits the rails. I don't yet see a way (in or out of loop) to add a follower in such a way that it affects the actual op-amp output pin level... The issue I face is that my circuit may well not be able to drive enogh so that Vin+ = Vin-.? When that occurs, I want the op-amp to give up, accept the desired Vout/Vin cannot be reached, and not start slewing at max rate to the rails. Regards Stephen. |
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Re: How can I make my simulation oscillate like my poorly designed PC board does?
¿ªÔÆÌåÓýThat sounds like you have a trace on your circuit that is acting as what used to be known as a Lecher line, but these days would be classed as a transmission line stub. ?
? At the critical point on the wave form this has a higher Q than the rest of the circuit and so the oscillation occurs. ? I can¡¯t help but get the feeling that increasing the miller capacitance is only helping it oscillate. Put about 10 ohms in series with the drain, close to the FET, and see what happens. A series resistor right at the gate might be an alternative stopper to oscillation. ? ? ? From: carlvanwormer@... [LTspice] [mailto:LTspice@...]
Sent: 29 May 2014 16:25 To: LTspice@... Subject: [LTspice] How can I make my simulation oscillate like my poorly designed PC board does? ?
I have a PC board with a FET that has a high-frequency oscillation because of my sloppy layout.? I'm trying to simulate the oscillation effect, but I'm unable to make my simulated circuit oscillate!? I know that most requests to the group are to stop the time-wasting oscillations in our simulations, ?but I need help making my circuit oscillate.? I've uploaded my circuit (Oscillating Miller FETs.asc) for your viewing pleasure. The goal of my final circuit is to slow down the rise and fall times with a large cap between the Drain and Gate, increasing the Miller Effect that we often try to minimize.? I usually tweak the value of the Miller Effect cap in the final circuit to balance the reduced noise switching harmonics (30MHz, for this design) with the increased heating losses of the slower switching speeds.? Unfortunately, I get a burst of oscillation (150-220MHz) about half way up the switching waveform on my circuit board.? I've traced the problem to a long trace to a poorly placed Miller Effect cap.? Any help in making my simulation oscillate would be appreciated. ? Thanks,
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thutches
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