mliccione89 wrote, "I'm not getting what I expect to see at the output of the TIA."

What did you expect to see?

It looks to me like you are sending very narrow (~ 2 ns wide) pulses into the TIA.? How much bandwidth is required to pass a 1 ns risetime?? The rule-of-thumb is at least 350 MHz.? How much bandwidth does the ISL70444SEH have?? Its datasheet claims that its GBP is 19 MHz typical -- which is much less than what you would need to maintain a reasonable likeness of your pulses with their 1 ns rise and fall times.? Perhaps it is acceptable to live with the lost rise and fall times, but I think the pulse widths are just too narrow to expect them to be faithfully reproduced by such a "slow" op-amp.

There are faster op-amps.? But it gets challenging to work with extremely fast op-amps.

Consider starting slow in your simulation (much wider pulsewidths at I1 and I2), and then watch at what point the output waveform can't keep up.

Andy

Richard wrote, "I just went to diodes.com and found the newest spice model for the?"

And ... what is your point?

That was one of the four BSS138 SPICE models that vedhaanth648 already pointed to, yesterday, when they asked their question.? What do you make of that one particular model, and why should we think it is either better or worse than other BSS138 SPICE models?

I think it's funny that you call this one "the newest spice model" when it is in fact 16 years old.? I found many other BSS138 models which are newer than that one.? So the "newest spice model" you found is definitely not newest!? Check your facts.

But as I said previously, newness does not imply goodness.

Just an FYI -- I have four BSS138 SPICE models from Diodes Inc.? And I've got three more from Onsemi, one from NXP, and six from Infineon.? What makes any model good?? I'd say it is how well it agrees with what the part actually does, which is best determined by purchasing a few dozen samples from various manufacturers, and hooking each one up to some test equipment.

Andy

Thanks Tony et al. I did totally flub the initial file upload. I've moved on to using this opamp for my intended purpose, as a TIA that can pass pulses from a photodetector. I'm not getting what I expect to see at the output of the TIA. Perhaps this opamp is not fast enough?

Here are the files

I just went to diodes.com and found the newest spice model for the

Then start with the simplest circuit of a single stage, then add stages until it disproves the conjecture.

Tim

On Thu, Jul 6, 2023 at 04:33 AM, Tim Hutcheson wrote:

I got the impression that the switching mechanism is essentially the same as he describes in a 2008 lecture on SCC, at ?where at about 55 minutes into the slides hew states just that.? So then I looked at the schematic in one of his students thesis for a small implementation and it seemed to confirm this.? I could be wrong.

IMO, you are wrong, Tim. The video is about a quasi-continuously varable step-down DC/DC converter.

Concerning his self-adjusting autonomous 4s battery equalizer, Sam Ben-Yaakov described a natural self-balancing behaviour (propagation indeed) permitting the use of 2 switches per cell in case it is acceptable that the 4s cells series-arrangement balancing takes 5 hours.?An LTspice simulation could validate this. Can an LTspice simulation show that a 104s arrangement behaves the same natural way?

It's quite sinple. One must to concentrate on




Regards,
Steph

On Thu, Jul 6, 2023 at 02:22 AM, Lohi Karhu wrote:

Funny thing is, that I filed a patent, way back in about 2007 on balancing ‘energy storage devices’ using a switched-capacitor mechanism…
US 7,994,756 B2

Nokia Corporation, unfortunately no series layout.

Richard wrote, "The files are dated, use the most recent one."

That's one way of thinking about it, but probably not the best.? Newer does not mean better.? You might get the one made by someone who just got out of high school and first used SPICE two weeks ago.??You could also base your decision on who made the model, or what company published it (may or may not be the same).? Preferably, you should try the models and compare them with datasheets, or with measurements of real parts.

Andy

The files are dated, use the most recent one.

vedhaanth648,

I uploaded your file for you.? It is in the Temp folder.? BSS138.zip.

To answer your question "i dont know which one to use", use whichever one you want to use.? All three of them appear to be SPICE models, so any of them should work in SPICE (and LTspice).? Take your pick.??They appear to be MOSFET models.? Two of them can be used directly.? But one of them (BSS138.lib) is a special model that has a fourth pin for temperature.? To use that one, you will need to create (or borrow) a special MOSFET symbol that has the fourth pin, and then use that pin correctly.? That might mean connecting the fourth pin to a voltage source, or to an RC network to represent a heatsink.

So I recommend starting with the other two models first.

The other two models are ordinary 3-terminal subcircuits.? You can use them with LTspice's normal MOSFET symbols (either NMOS or PMOS as appropriate).? After adding the symbol to your schematic, then use Ctrl-right-click on the symbol, and change the Prefix value to "X" (without the quotes), and click OK.

Andy

Please do not point us to some random website that has your files, even if it is your own.? UPLOAD your files to our group's Files section, into the "Temp" folder:

? ??/g/LTspice/files/Temp

Maybe you forgot to read what it says on the group's main webpage: "do not point us to other ("third party") file storage websites".? Go back now and read the group's main webpage.

Andy

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Please DO NOT send us to third-party sites for data. Upload your .ZIP to Files => Temp, and then tell us you did that. Meanwhile, you mean BSS138, not BS138.? The way to add third-party models is explained in the Help, but it's best to put the model file in the same folder as the .ASC. Don't try to add it to LTspice's native files, which is not straightforward and often leads to problems.

i have the following 3 files related to it.

i dont know which one to use

and which standard component to use in place of this component

OTOH, we don't even need a calculator to compute the MTTF of such a circuit.

-marcel

Tim wrote, "Yikes, my calculator says that's more than? 2.028e31 switches."

That could be a challenge even in LTspice.

At the end of the day, subcircuits don't make simulations smaller.? If there are 2.028e31 switch subcircuits, they are not represented by one subcircuit that gets 'called' 2.028e31 times.? They have to be expanded into 2.028e31 equivalent circuits that become part of the full netlist.? That's a lot of transistors and more.

I don't think today's PCs are quite capable of that.? ;-)

Andy

I got the impression that the switching mechanism is essentially the same as he describes in a 2008 lecture on SCC, at ?where at about 55 minutes into the slides hew states just that.? So then I looked at the schematic in one of his students thesis for a small implementation and it seemed to confirm this.? I could be wrong.

Tim

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On 06/07/2023 11:02, garvind25@... wrote:

Pls read the value of Cox as 8.5fF/um^2. It is the oxide capacitance per unit area. While implementing the formula fT = gm/2*3.14*W*L*Cox, W and L are MOSFET sizes in um.

?

The y-axis is in ohm-1 (ohm inverse or siemens). This is the unit of gm. In other words, while implementing the above fT formula, the y-axis is taking the units of gm only. It should be of frequency (in Hz or KHz etc)

In the Files section of the group's archives, there is a demo schematic that shows how to plot Ft vs. Id. Once you understand how it works, you can adapt it to .MEASure gm as well as Ft, then you can also plot Ft vs. gm.

Funny thing is, that I filed a patent, way back in about 2007 on balancing ‘energy storage devices’ using a switched-capacitor mechanism…
US 7,994,756 B2

have a fine day, all…

Barry Rowland
Just a simple ?? guy in ??...

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On 06/07/2023 10:54, Tony Casey wrote:

In .AC plots, Freq(uency) and Omega are also recognised.

I forgot: in .TRAN plots, "time" is also recognised. See:

Help ?? LTspice XVII ?? Waveform Viewer ?? Waveform Arithmetic

..for definitive information.

Thanks for the quick reply. Pls find below the answers to your queries:

?

Pls read the value of Cox as 8.5fF/um^2. It is the oxide capacitance per unit area. While implementing the formula fT = gm/2*3.14*W*L*Cox, W and L are MOSFET sizes in um.

?

The y-axis is in ohm-1 (ohm inverse or siemens). This is the unit of gm. In other words, while implementing the above fT formula, the y-axis is taking the units of gm only. It should be of frequency (in Hz or KHz etc)

?

Thanks again,

Arvind Gupta

?