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Janiel Feng <m_zhao12@...> wrote:

I imported models from Pspice to LTspice from TI and Analog Devices. But most
of them have Convergence Problem. Is there anybody know how to solve this problem?

First, try some of the FAQ files located here:

Files > FAQ
()

In particular, look at "Simulator_options.txt". Also look at
"faq_14.txt" and search for "convergence".

Andy

Janiel Feng <m_zhao12@...> wrote:

I imported models from Pspice to LTspice from TI and Analog Devices. But most
of them have Convergence Problem. Is there anybody know how to solve this problem?

You should have created a new message topic with its own Subject,
rather than hijacking someone else's question.

Response forthcoming with a new Subject line.

Andy

Hi,

I imported models from Pspice to LTspice from TI and Analog Devices. But most
of them have Convergence Problem. Is there anybody know how to solve this problem?

Thanks.

Janiel

Dear Michael, Thanks.
Of course example but Helmut make sense (a modified version is here: ) in time domain.

But, I don't want to be in time-domain. All I wish is a frequency domain plot.
Also, expressing R2 as R2(f) is perhaps not suitable in my case. one doesn't write for example, a sinusoid voltage as V(f) because sinusoid is a single frequency signal. so consider R2 as a single frequency 'signal'.
Just as you plot Bode to know how the output voltage changes as the frequency of input voltage changes, I wish to know how the output will changes if the frequency of variation of R2 changes.

I have gone through many books on circuit analysis; they all talk in terms of input/ouput as a voltage or current signal.

Hello Helmut. Thank you for your example. I have no issue in performing transient.
Question is how do I simulate this behavior in terms of frequency response.

The quickest way to get a frequency response is to use an .AC
analysis, rather than .TRANsient. Then you can sweep and plot output
amplitude versus frequency.

The thing to always remember about .AC analysis, is that it is a
"small-signal" analysis, and the entire circuit is first linearized at
the operating point. If there is anything nonlinear in your circuit,
its effects would be ignored.

For the op-amp circuit, if you want to see the response from resistor
R2 to the output, that should work. But if you want to do something
like look at the frequency response between the source VDC and the
output, while R2 varies sinusoidally, that would not work because R2
modulates the response, i.e., its effect on VDC (and vice-versa) would
be nonlinear.

The other possible problem with .AC analysis is getting a modulated
resistance that works in AC analysis too.

Sometimes you just need to use a transient analysis. Then you can use
the .STEP command to vary the frequency in steps.

Andy

Hi Maktoomi

Helmut example is absolutely right. This is because a quick analysis of the circuit you have given shows the following:-

Vo/Vin = R2(f)/R1 . It follows that Vo= [R2(f)/Rin]*Vin = Iin*R2(f)

Now Vo = Iin*R2(f) shows the variation of the output with increasing frequency for a simulation time of 100mS. It does not take a lot of imagination to deduce that if your inverting amplifier can be represented by a single exponential lag, Vo will follow the response shown by Helmut's example and then its envelope will roll off at 20dB per decade at high frequencies at the half power point. You can sketch this manually when you know the frequency response of the inverting amplifier you want to use from the data sheet. (refer to Bode). Once you define your R2 the rest is easy.

Best regards,

Michael P Kiwanuka




To: LTspice@...
From: amaktoomamu@...
Date: Sat, 13 Apr 2013 16:46:27 +0000
Subject: [LTspice] Re: inverting opamp simulation: rapid component variation






Hello Helmut. Thank you for your example. I have no issue in performing transient. Question is how do I simulate this behavior in terms of frequency response.
I want to see how output varies if the rate of variation of R2 keeps on increasing. So, I wish to get a plot Vout vs frequency, where frequency shows the rate of fluctuation of R2.
Higher the frequency on horizontal scale, more rapid the variation in the value of R2.

Any help/suggestions would be greatly appreciated. (This is a part of a paper that I aim at submitting in conference).

PS: I have posted similar question in edaboard to get help in manual analysis of this problem.( more details: )

--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:

--- In LTspice@..., "MOHAMMAD A MAKTOOMI" <amaktoomamu@> wrote:

Hi,
In an inverting amplifier(Uploaded File:
),
suppose R2 fluctuates very rapidly (say at 10KHz or even
higher, may be due to some environmental condition).
How do I simulate this behavior, given input is some fixed
dc voltage and opamp is 741 type (I have not attached any
specific opamp model so far, use what you have).
I am basically interested in perhaps frequency response-
I want to see how output varies if rate of variation of R2
keeps increasing.

Hello,

I have uploaded an example with a time-variable resistance.

R=1k+5k*(V(ctrl)+1)

Files > Temp > ni-opamp_.asc

Best regards,
Helmut

[Non-text portions of this message have been removed]

I am new to LTspice and electricity(my dad is my teacher), I was looking on
google how to add a photo transistor. The only useful thing I found was to add
a Photo coupler. I tried this in a circuit with a n-Channel mosfet and it was
successful. But when I want to change the parameters of the Photo coupler
it gives me a notification it is not possible. How can I override this?

This is likely a MS-Windows problem, but you haven't given us nearly
enough information to say for sure.

You probably put a file in a directory owned by Windows (perhaps a
subdirectory of C:/Program Files/ where the LTspice program itself
is), and Windows doesn't let you modify it. Morale: Never put your
schematics, models, symbols, subcircuits, or netlists under the
Program Files folder.

If your interpretation of "it is not possible" differs from mine, then
maybe I am not on the right track. If so, you will have to give us a
lot more information. Or, upload your file(s) as instructed on this
group's main page and show us what didn't work.

Regards,
Andy

Hello.
How to calculate, using maths and definitions, the THD of this signal: A sine with a small dent at the crossovers.

S(t) = 0 for 0 < t < D where D is much smaller than T
S(t) = sin omega*t for D < t < T/2 where omega is 2*pi/T
S(t) = 0 for T/2 < t < T/2 + D
S(t) = sin omega*t for T/2 + D < t < T

Using LTspice simulations I find THD = 25*( D/T )^2
In this simulation I used a 1000 HZ SINE combined with a PULSE with values of D like 0.1u 0.2u 0.5u 1u 2u 5u 10u 20u 50u
These simulations gave me a THD that perfectly fits with 25*( D/T )^2

Here is the issue.
I was enable to prove this result with maths
(instead of simulations ).
I started computing the RMS value of the error signal (the dents at the crossovers)
With sin omega*t = omega*t ( valid for t << T )
I don' t get the 25*( D/T )^2 result, I do get a fonction of D/T, so far so good, but I don't get the right exponant. It seems my approach is wrong.

Is there a signal theory / maths guru who can give the proof that for such a signal S(t) ( with D << T ) we have THD = 25*( D/T )^2

Dear all,

I am new to LTspice and electricity(my dad is my teacher), I was looking on google how to add a photo transistor. The only useful thing I found was to add a Photo coupler. I tried this in a circuit with a n-Channel mosfet and it was successful. But when I want to change the parameters of the Photo coupler it gives me a notification it is not possible. How can I override this?

Many thx. for your feedback,

Kr,

Renato

Hello Helmut. Thank you for your example. I have no issue in performing transient. Question is how do I simulate this behavior in terms of frequency response.
I want to see how output varies if the rate of variation of R2 keeps on increasing. So, I wish to get a plot Vout vs frequency, where frequency shows the rate of fluctuation of R2.
Higher the frequency on horizontal scale, more rapid the variation in the value of R2.

Any help/suggestions would be greatly appreciated. (This is a part of a paper that I aim at submitting in conference).

PS: I have posted similar question in edaboard to get help in manual analysis of this problem.( more details: )

In message <kkbun5+ctqn@...>, dated Sat, 13 Apr 2013, Tim <thutches@...> writes:

I just uploaded a another copy of the JT, because I wnat to use it as a techng aid to introduce a family member to some EE concepts and LTspice. He just graduated high school and has no exposure but a lot of interest in electronics.

Too late! You need to start at Grade 2 or earlier. (;-)

So having read the recent thread on the JT, I though it might be an excellent resource for him as it exposes transistor and switching theory and a lot of concepts in an easy to understand project that he can build and use my lab tools to verify the expected behavior.

It may be me, but I don't find non-linear oscillators at all simple.

In my posted version, derived from , I tried to added a second circuit to compare the effects of using a different transistor than the B549 in the reference article and I attempted to estimate the Joules being consumed (atfter all it is a Joule Thief.

If anyone cares to comment on how I might do this better (for the intended purpose), please do so.

I favour sine-waves and audio frequencies, but we are all different.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
They took me to a specialist burns unit - and made me learn 'To a haggis'.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

All,

I just uploaded a another copy of the JT, because I wnat to use it as a techng aid to introduce a family member to some EE concepts and LTspice. He just graduated high school and has no exposure but a lot of interest in electronics.

So having read the recent thread on the JT, I though it might be an excellent resource for him as it exposes transistor and switching theory and a lot of concepts in an easy to understand project that he can build and use my lab tools to verify the expected behavior.

In my posted version, derived from , I tried to added a second circuit to compare the effects of using a different transistor than the B549 in the reference article and I attempted to estimate the Joules being consumed (atfter all it is a Joule Thief.

If anyone cares to comment on how I might do this better (for the intended purpose), please do so.

Thanks,

Tim

--- In LTspice@..., "MOHAMMAD A MAKTOOMI" <amaktoomamu@...> wrote:

Hi,
In an inverting amplifier(Uploaded File:
),
suppose R2 fluctuates very rapidly (say at 10KHz or even
higher, may be due to some environmental condition).
How do I simulate this behavior, given input is some fixed
dc voltage and opamp is 741 type (I have not attached any
specific opamp model so far, use what you have).
I am basically interested in perhaps frequency response-
I want to see how output varies if rate of variation of R2
keeps increasing.

Hello,

I have uploaded an example with a time-variable resistance.

R=1k+5k*(V(ctrl)+1)

Files > Temp > ni-opamp_.asc

Best regards,
Helmut

Hi,
In an inverting amplifier(Uploaded File: ), suppose R2 fluctuates very rapidly (say at 10KHz or even higher, may be due to some environmental condition). How do I simulate this behavior, given input is some fixed dc voltage and opamp is 741 type (I have not attached any specific opamp model so far, use what you have).
I am basically interested in perhaps frequency response- I want to see how output varies if rate of variation of R2 keeps increasing.

--- In LTspice@..., "thomas.lafay" <thomas.lafay@...> wrote:

Greetings.

How can I find the max or min of a .measure command from a Monte Carlo run?

my command --> .measure dc trans find I4 when V(N016,N002)=0

Question: how to find the max or min of the data?

Many thanks, Tom.

Hello Tom,

You could plot the results from .MEASURE
View -> SPICE -> Error log
Right-mouse-click -> Plot Stepped data

You could also copy the results(numbers) from the Error Log
file to any math- or spreadsheet program to analyze the data.

Best regards,
Helmut

Greetings.

How can I find the max or min of a .measure command from a Monte Carlo run?

my command --> .measure dc trans find I4 when V(N016,N002)=0

Question: how to find the max or min of the data?

Many thanks, Tom.

--- In LTspice@..., á???????? ?????????× <BordodunovAlex@...> wrote:

Hi John Woodgate.
Thanks for the info. In my Standard.zip file is 2N242 and germanium transistors 2N2955. Using these models and your information I will make models of transistors AC128 AC127 more believable.
Bordodynov.

I don't see either of these in the standard library. I placed a pnp in a new schematic then right-click Pick New Transistor. I just did a sync release too. Decades ago 2N2955 was a silicon part (complementary to 2N3055).

Jim

How to use .param and .tran simulation in LtSpice?

Please show its use in this question-

Use SPICE to plot the output characteristic for NMOS transistors with
different Length's (constant W/L). For each curve, use the waveform viewer
to plot the small-signal output resistance, r0, hence verify the theoretical
dependence of trans-conductance on Length that you have studied in
class. Use minimum feature size of 0.18μm.

This is a homework assignment, right?

Let me ask you this: Did you go to college to learn how to do those
things yourself, so that you can become a good engineer, or are you
looking for free handouts so you never need to do the work yourself?

If the latter, you should be shamed into failing the assignment.

Show us what YOU have done so far on this problem. You should have
figured out most of it already.

This is a forum where people help others who first make an attempt to
do their work but run into something that doesn't work right. It is
not where answers to homework assignments are handed out to losers who
cannot be bothered to try. Are you one of those?

One of the first pieces of advice I give many people about using
LTspice, is to use it like they would if they had real parts on the
bench. Let's say someone handed you some NMOS transistors and you had
access to power supplies and DVMs and oscilloscopes. What would you
do with them to characterize the transistors? Start by making LTspice
do the same things.

Andy

SPICE models for INA193 and AD8210 are available in the web site of TI
and Analog Device respectively.
Regards.
Varoli

--
Prof. Vincenzo Varoli
Politecnico di Milano Dip. Energia
Via G. Ponzio 34/3 I20133 Milano Italia
Tel. 0223996393 FAX 0223996309

Hello,

is there anywhere a model for a bridge current sensor available for downloading?

Thanks
Mario