Re: Build spice model of transimpedance amplifier
On Tue, May 21, 2024 at 03:23 PM, Mirza wrote:
OPA855
* OPA855 - Rev. A * Created by Sean Cashin; 2020-06-04 * Created with Green-Williams-Lis Current Sense Amp Macro-model Architecture * Copyright 2020 by Texas Instruments Corporation
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For Spice it did not applied for FET but for BJT.? Can be used for oscillator and filter built using op-amp?
On Monday, 20 May 2024, 21:52:54 GMT+4, <mhx@...> wrote:
("AI Detector for ChatGPT, GPT4, Gemini") identifies the (first two) texts as
100% AI-generated (then I got bored). However, I don't think we need scribbr to tell us they're worthless :--)
LinkedIn thinks it has found a way for the AI copyright infringement barrier when attempting to scavenge
deep insights on specialized subjects. They might even have optimized out the 'prompt engineer.'
-marcel
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Re: Build spice model of transimpedance amplifier
On Tue, May 21, 2024 at 09:49 PM, Andy I wrote:
Mirza, I'm assuming that you want an actual purpose-built transimpedance amplifier, one that has everything in it already.? Right?? They are considerably less common than ordinary op-amps, of course.? I wonder what characteristics other than "very high speed" that your TIA needs.
Yeah I want an actual purpose-built transimpedance amplifier like OPA855 from Texas Instruments, LTC6268-10 from Analog Devices. However, these can not meet my bandwidth requirements for gate mode circuit (in my case). Thus, I am looking for spice models from other companies, however, they do not have (or provide) spice model for their high speed TIA. According to your comments "It is possible to make a generic TIA model, but probably not easy to make one that mimics characteristics of an actual part. ?The answer depends on how closely you need the model to approach the actual part. ?A generic model would lack things like nonlinear behavior. ?Datasheets might not tell you enough about that. ?But that's just my opinion." Yeah I feel that you are right.
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Re: Conditional PWL Current Source
eewiz wrote:
Prior to your suggestion, I did not know that .param statements could do IF().
This opens a whole new world of controllability that I had not previously understood.
It helps here to read the Help page for the .PARAM command.? It is all documented there. There might be other shortcuts for temporarily disabling the PWL() section for running a simulation, if that is what you are trying to do.? One is to use a parameter for the "high" current level, instead of 1 Amp.? Then change only the parameter assignment.? Another one, though somewhat kludgy, is to right-click on the PWL text next to the current source, and change it from this: ? ? pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0 +11.99998m 0) endrepeat)to this: ? ? 0 ; pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0 +11.99998m 0) endrepeat)by adding "0 ;" before the PWL() part.? The ";" character is a comment character.? LTspice ignores everything after it.? So that changes it from a PWL current source to a 0 Amp source, while leaving all the text still in place where it can be restored later. Andy
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Re: Conditional PWL Current Source
Hello All,
?
Tony, thank you.
Mine was the latter.
I simply need to disable the four pacing current sources, and maybe enable others, before running the sim.
I tried doing IF() inside the PWL statement and that did not work.
Prior to your suggestion, I did not know that .param statements could do IF().
This opens a whole new world of controllability that I had not previously understood.
?
Thank You
?
Sent:?Tuesday, May 21, 2024 at 7:20 AM
From:?"Tony Casey via groups.io" <tony@...>
To:[email protected]
Subject:?Re: [LTspice] Conditional PWL Current Source
On 21/05/2024 12:03, eewiz via groups.io wrote:
pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0 +11.99998m 0) endrepeat)
I-sources cannot be behavioural, thus cannot be changed while the analysis is running. Do you need to do that, or can your analysis be .stepped with different conditions applied to each step?
If the latter:
pwl(0 0 48.2m 0 repeat forever (0 0 +20n {OnCurrent1} +11.99998m {OnCurrent1} +20n 0 +11.99998 0) endrepeat)
..
.param OnCurrent1 if(Condition1, 1, 0)
..
..etc
If you want to change dynamically, you will have to use B-sources, or a switch matrix. I uploaded a version using a switch that might meet your need.
If you have complex combinatorial conditions, you might want to read up on the State Machine feature.
?
--
Regards,
Tony
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Re: How to modify the Positive Threshold Voltage on ltspice built-in component?
Leon wrote, " just setting the vt and vh on the spice line,right?" Yes, they can go on any of these lines:
- Value
- Value2
- SpiceLine
- SpiceLine2
If there is no value for "vt" then it defaults to (Vhigh+Vlow)/2. Put an "X" in the "Vis." column (by double-clicking there) to also make that attribute visible on the schematic. Andy
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Re: Build spice model of transimpedance amplifier
marcel wrote, " (OPA170 PSpice lib file)."
Of course that is an ordinary op-amp, not a transimpedance amp.
Most op-amps with feedback turn into transimpedance amps, so you might say that every op-amp can also be a transimpedance amplifier.
Mirza, I'm assuming that you want an actual purpose-built transimpedance amplifier, one that has everything in it already.? Right?? They are considerably less common than ordinary op-amps, of course.? I wonder what characteristics other than "very high speed" that your TIA needs.
Andy
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Re: How to modify the Positive Threshold Voltage on ltspice built-in component?
Leon,
I did as you did in your photo (ΞĻ”XÈ¡®‹Ãæ 2024-05-21 174809.png), and it worked for me.
Of course since it is a Schmitt device, it has hysteresis so it has different actual thresholds (not quite at 50%) for rising and falling edges, unless you also changed Vh (hysteresis) to 0.
Andy
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Re: Build spice model of transimpedance amplifier
Oddly, some of (what are now) Analog Device's TIAs do not seem to show up within their TIA section of the product selection pages, making their product selections incomplete.
I might be wrong, but it appears that ADI has rearranged their product selection pages and made them more difficult to navigate, as well as incomplete and maybe wrong.? Arrgh!
Andy
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Re: Build spice model of transimpedance amplifier
Mirza wrote, "Yeah I know that LTspice has several op amps."
No, that's not what I said.? What I said is that LTspice has transimpedanca amps, which are not op-amps.? Do any of Analog Device's transimpedance amps meet your requirements?
Did you look them up in LTspice?
I'm NOT talking about op-amps, even though you might find their SPICE models within the [OpAmps] section of LTspice.
Andy
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Re: Conditional PWL Current Source
On 21/05/2024 12:03, eewiz via groups.io wrote:
pwl(0
0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0
+11.99998m 0) endrepeat)
I-sources cannot be behavioural, thus cannot be changed while the
analysis is running. Do you need to do that, or can your analysis be
.stepped with different conditions applied to each step?
If the latter:
pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +{OnCurrent1} 1 +20n 0
+{OnCurrent1} 0) endrepeat)
..
.param OnCurrent1 if(Condition1, 1, 0)
..
..etc
If you want to change dynamically, you will have to use B-sources,
or a switch matrix. I uploaded a version
using a switch that might meet your need.
If you have complex combinatorial conditions, you might want to read
up on the State Machine feature.
--
Regards,
Tony
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All,
The VISHAY VOMDA1271 device simulates correctly.
The VISHAY LH1262 device fails due to a defective spice model.
The VISHAY VO1263 device fails due to a defective spice model.
I have submitted all of my simulation files to VISHAY and requested that they correct their spice files.
I will post a reply when I receive a response from VISHAY.
Mike
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Re: How to modify the Positive Threshold Voltage on ltspice built-in component?
sorry, i think i find the solution??
just setting the vt and vh on the spice line,right?
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Conditional PWL Current Source
Hello All,
?
I have four PWL current sources that drive a half-dozen switches to simulate the outside world.
The PWL current sources and switches push my simulation through its paces.
I would like to parallel aditional current sources to switch certain functions on or off differently from the standard paces that the four original PWL current sources provide.
All current sources are 0A or 1A and have 1 Ohm parallel resistors to cause a 0V or 1V output.
?
For example, one current source runs on:
pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0 +11.99998m 0) endrepeat)
I would like to parallel an additional current source that, as simply as possible, runs on:
IF(V(test)>0.5, 1, 0), probably a B source could be used here.
In this way, the signal V(test) should shut down the PWL current source and at the same time fire up the continuous current source.
What I can't figure out is how to get an externally controlled PWL current source that either does its PWL thing or zero output.
?
Having to remove the four PWL strings to shut down the PWL current sources is too error prone.
?
I tried to control the example PWL current source above, like this but, it does not work:
if(V(test)<0.5, pwl(0 0 48.2m 0 repeat forever (0 0 +20n 1 +11.99998m 1 +20n 0 +11.99998m 0) endrepeat), pwl(0 0))
It produces the error "Missing current value for I1".
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I checked the help for behavioral sources and see no mention of PWL for a B source.
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Any ideas?
?
Thank You
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Re: How to modify the Positive Threshold Voltage on ltspice built-in component?
On 21/05/2024 11:46, Leon show wrote:
i want to
invert a high level voltage through schmitt inverter , but the
data spec show the high level threshold is not as ltspice original
setting 50%, so can anyone teach me how to modify the threshold??
where can i give the command or modify the parameter?
You might find this useful:
Help > LTspice > LTspice? > Circuit Elements >
A. Special Functions > 1st Section
--
Regards,
Tony
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How to modify the Positive Threshold Voltage on ltspice built-in component?
Hello, everyone?
i want to invert a high level voltage through schmitt inverter , but the data spec show the high level threshold is not as ltspice original setting 50%, so can anyone teach me how to modify the threshold?? where can i give the command or modify the parameter?
thanks a lot !!!!
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Re: Build spice model of transimpedance amplifier
(OPA170 PSpice lib file).
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Re: Build spice model of transimpedance amplifier
Yeah I know that LTspice has several op amps. Probably all are from Analog Devices, right?
I contacted some manufacturers and they replied that they do not have SPICE models.
Thank you very much.
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Re: Build spice model of transimpedance amplifier
If I search the group's Files for "TIA", several things come up, not all of which are for TIAs.? And that doesn't include transimpedance amps that don't use the "TIA" abbreviation.
If you have a particular TIA model in mind, search our group for the model name to see if anyone else has used it already.
Andy
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Re: Build spice model of transimpedance amplifier
You asked about making a TIA model from scratch - but did you know that LTspice has some TIAs already?
Also, are you certain that the other manufacturers do not have SPICE models?? Some manufacturers make it challenging to find models when they are there.? Navigating websites has become challenging, IMO.
It is possible to make a generic TIA model, but probably not easy to make one that mimics characteristics of an actual part.? The answer depends on how closely you need the model to approach the actual part.? A generic model would lack things like nonlinear behavior.? Datasheets might not tell you enough about that.? But that's just my opinion.
Andy
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eewiz
Tony Casey
Leon show