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--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:

I think what's happening here is that your circuit has two possible stable
states, due to the fact that it has no real V+ supply voltage. If the
op-amp happens to start up yanking on the output pin, it will pull the
positive supply pin voltage down with it so that it goes low, and then it
settles on that second stable operating point, with the output pin
negative. In that state, the op-amp is open-loop and essentially broken.

If that doesn't happen, it lets the output pin (and the positive supply
voltage) go high, and the negative feedback works normally.

With it being a roll-of-the-dice which stable state comes up, a change to
one part of the circuit can cause a change elsewhere.

To prove that there are (at least) two stable states I did the following.

I added a .NODESET V(n010)=10V to the circuit where U1 was replaced by the
UniversalOpamp2, and this makes U2 come up "normally" again.

I tried adding a .NODESET V(n010)=-2.5V to the un-modified circuit. This
seems to cause LTspice to go into spasms where it can't find a clean
operating point to start the transient simulation with, but it runs anyway
and the transient simulation waveforms indicate that it doesn't ever
recover to the "normal" situation where there is a good positive supply
voltage. In other words, it finds the second stable operating point where
U2 is open-loop, and its output remains low.

This is a very poorly behaved negative feedback circuit. Highly
questionable design.

Regards,
Andy


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

That's great detective work and analysis! You've shown me a new tool to use in future troubleshooting attempts.

Yes, I know the circuit is strange . . . I inherited it from a customer and was running some simulations in order to understand the functions and problems. The reason for the strangeness is that it runs a the end of a long twisted pair, and the power line is also the signal line. I added the -5V negative rail in an attempt to get the simulation running, since the opamp I selected drew 5 times the current of the part they were using, unbalancing the design. I may try to give them an alternate power+signal 2-wire design that is inherently stable.

Thanks,
Carl

Hi Helmut,

Thanks again. I'll take another look at it and see if this time the penny drops :-)

Greetings,

Jesper

Hello Ross,

unfortunately neither by Analog Devices nor in the internet is a .subckt ADCMP566 to find.

:-(

Leo

Hi does anyone have a model for the ADCMP566 comparator
regards
Ross

Hi Ferdian Cahyodwiputro.
You gave yourself the problem from scratch.
Using the command ". Inc" or ". Lib" you have to enter into it full name.
In my electronic circuit: .inc 2SC5006.txt.
If you like the LIB file extension, then copy my file 2SC5006.txt to a file 2SC5006.lib.
Bordodynov.

11.07.2013, 11:42, "Ferdian Cahyodwiputro" <ferdiancahyodwiputro@...>:

Hi Mr.Александр Бордодынов

i was download your file but cannot open in LTspice because format not .lib.
can you upload again with format .lib for component transistor 2SC5006?



________________________________
From: Александр Бордодынов <BordodunovAlex@...>
To: "LTspice@..." <ltspice@...>
Sent: Wednesday, July 10, 2013 7:53 PM
Subject: Re: [LTspice] low noise amplifier



?
Hi Ferdian Cahyodwiputro.
I created a small electronic circuit to test the model. Using this scheme, I found that the description of the transistor pins are in non-standard order. I will put circuit in the TEMP folder.
Bordodynov.

10.07.2013, 15:33, "Ferdian Cahyodwiputro" <ferdiancahyodwiputro@...>:

Hi Mr. Александр Бордодынов
can you upload this component? because i still can't understand to create new component..
i'm still newbe

________________________________
From: Ferdian Cahyodwiputro <ferdiancahyodwiputro@...>
To: "LTspice@..." <LTspice@...>
Sent: Wednesday, July 10, 2013 6:22 PM
Subject: Re: [LTspice] low noise amplifier

thank you..

this conversation helpfull my trouble.

________________________________
From: Александр Бордодынов <BordodunovAlex@...>
To: "LTspice@..." <ltspice@...>
Sent: Wednesday, July 10, 2013 5:06 PM
Subject: Re: [LTspice] low noise amplifier

==>HELP==>F.A.Q==>Third-party Models-->
.....
Example for a 3-pin NPN transistor but defined with a .SUBCKT statement:
.....

Bordodynov.

10.07.2013, 13:55, "Ferdian Cahyodwiputro" <ferdiancahyodwiputro@...>:

thank you for your information by the way so i must create new design symbol with this parameter?

________________________________
From: Александр Бордодынов <BordodunovAlex@...>
To: "LTspice@..." <ltspice@...>
Sent: Wednesday, July 10, 2013 12:21 PM
Subject: Re: [LTspice] low noise amplifier

Hi.
Model:

.SUBCKT q2SC5006_v111 7 8 9
Ccb 2 5 58f
Cce 2 6 87f
Cbe 7 9 0.67f
Cb 1 2 180f
Ce 2 3 180f
Lb 5 7 1.09n
Lc 2 8 0.79n
Le 6 9 0.99n
Lb2 1 5 0.004n
Le2 3 6 0.004n
Qnpn 2 1 3 q2SC5006_v111_M

.MODEL q2SC5006_v111_M NPN
+(IS=616e-18 BF=161 NF=0.99 VAF=50.0
+ IKF=1.5 BR=14.4 NR=0.99 VAR=2.4
+ IKR=0.32 ISE=38.2e-14 NE=2.19 ISC=80e-17
+ NC=1.0 RB=4.37 IRB=759e-6 RBM=2.23
+ RE=0.4 RC=5.0 CJE=2.21p VJE=0.954
+ MJE=0.408 CJC=1p VJC=0.667 MJC=0.408
+ XCJC=0.8
+ FC=0.50 TF=20.0e-12 XTF=1e-3 VTF=0.668
+ITF=9.7 TR=0 PTF=40 EG=1.11
+ XTI=3.0 XTB=0)
.ENDS q2SC5006_v111

Bordodynov.

10.07.2013, 08:20, "ferdiancahyodwiputro" <ferdiancahyodwiputro@...>:

dear everyone
i have toruble to design low noise amplifier.
i search transistor 2SC5006 in library LTspice but i can't found it.
please help me how to get transistor 2SC5006 in library LTspice

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

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

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

I think what's happening here is that your circuit has two possible stable
states, due to the fact that it has no real V+ supply voltage. If the
op-amp happens to start up yanking on the output pin, it will pull the
positive supply pin voltage down with it so that it goes low, and then it
settles on that second stable operating point, with the output pin
negative. In that state, the op-amp is open-loop and essentially broken.

If that doesn't happen, it lets the output pin (and the positive supply
voltage) go high, and the negative feedback works normally.

With it being a roll-of-the-dice which stable state comes up, a change to
one part of the circuit can cause a change elsewhere.

To prove that there are (at least) two stable states I did the following.

I added a .NODESET V(n010)=10V to the circuit where U1 was replaced by the
UniversalOpamp2, and this makes U2 come up "normally" again.

I tried adding a .NODESET V(n010)=-2.5V to the un-modified circuit. This
seems to cause LTspice to go into spasms where it can't find a clean
operating point to start the transient simulation with, but it runs anyway
and the transient simulation waveforms indicate that it doesn't ever
recover to the "normal" situation where there is a good positive supply
voltage. In other words, it finds the second stable operating point where
U2 is open-loop, and its output remains low.

This is a very poorly behaved negative feedback circuit. Highly
questionable design.

Regards,
Andy

I'm trying to find an easy way to see if my signal saturates any OpAmp output, or violates some level to the next stage.

Right now, I'm using input values predetermined from matching to the existing breadboard circuit I know the levels are ok, but now I want to redesign using simulation.

Problem is...I have a VERY complex time input signal yet has fairly 'flat' harmonic content, so historically I have been able to use AC analysis and get very accurate simulation. for example, a representative data point using most recent LTspice I predict 35 ppm noise at 1kHz [that is, noise to signal levels] and MEASURE 36 ppm. So am very happy with the simulation and models. [the noise pretty much matches within 10% over the rest of the spectrum]

Here is the problem. I want to redesign the circuit, but not build it to verify operating levels. So how do I bounce between this frequency domain and the time domain WITHOUT taking days for each run?

What I mean is, I can represent the input waveform in a .wav form or PWL model, but we're talking 4400 UNIQUE data points that repeat and repeat. then, do .tran analysis, but that takes iteration after iteration to get a stable repeatable output signal.

Or, I could 'post-process' an AC analysis by just 'assuming' everything is copacetic, run the AC analysis, and find the harmonic values/phase angles and use octave to plot the signal. And, octave will tell me if I've violated maximum signal level.

How do I make the AC simulation put out specific frequency/phase values, maybe not the ones it used during the AC analysis? And how accurate will they be? The signal may be complex enough that a few degrees could cause a catastrophe, but I guess I could cross that bridge later, getting close right now would be a big help.

Is there a way to make a file of table of results? I give frequency points [not in the AC anlayis] and LTspice gives me amplitude/phase in a file, so I can run that through octave. Is there a way to 'force' the frequency data points of LTspice - there's a lot fo them?

Or, is there a way to stay in the time domain easily quickly generate the waveform as I change a component value someplace?

Help!

I have a circuit that uses an LT1702. To test some variations, I cloned that circuit so there are currently a pair of identical isolated circuits, both giving the same results (10.4V on the outputs of both opamps). If I change one of the opamps to a UniversalOpamp2, the other LD1702 output drops to about -3V, even though that circuit has not changed. I don't think I have any explicitly named nets that tie the two cloned circuits together. I'm running the current release (4.18j).
I've uploaded the original circuit to the Temp folder. If somebody could give it a try, here is my suggested process:
1. Run the circuit, verify that the opamp output pins are at about 10.4V
2. Delete one of the opamps, and then add a UniversalOpamp2 in its place
3. Run the circuit and check the output of the LT1702 (about -2V, unexpected change) and UniversalOpamp2 output (8.3V, expected because of biasing)

Thanks,
Carl

Hmmm, load dumps can last a looong time.

Hmm, I missed that, even though it was there in the Subject. I was
thinking that small stuff like ignition noise was all the suppressor diode
had to handle. My bad. :-)

Andy

Load dump can last for a long time. TVS is NOT generally used for load dump protection, just because of that. Instead, the emphasis is on using components (capacitors and voltage regulators) that will withstand 65V or more for something on the order of 1 second. What you CAN do is add a PTC "fuse" ahead of the TVS. That will limit the current and the power dissipated by the TVS.


National Semiconductor (now TI) has several linear regulators that are designed especially for this. Linear has, I believe, a number of switchers that are designed for automotive application and are spec'd this way.


Jim Wagner
Oregon Research Electronics

Hi Andy


On 07/10/2013 12:10 PM, Andy wrote:

The TVS may be sufficient. Like you say, they are meant to handle short
spikes, and that might be all that it ever sees ... ignition noise and
such. The instantaneous power could be up there but it's not wide enough
to heat up the device. The simulated waveform is probably very
pessimistic.

Hmmm, load dumps can last a looong time.
The large inductance field has to decay before
the alternator stops producing the over voltage.
100s of mS, long enough to fry the TVS?

Sorry for continuing OT.

Al D.


--


AC2CL

I do not think there is any thrill that
can go through the human heart like that felt by the inventor as
he sees some creation of the brain unfolding to success...
Such emotions make a man forget food, sleep, friends, love, everything.

- Nikola Tesla

--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:

I'm not quite sure what you are trying to achieve with that
expression, but I hope you know what you are doing there.

Er, um... homework?
___________________________

The invasion has begun... "Uhg-uhg. Brains, I need brains [drool]"

LTspice DOES NOT generate values at uniform sample times. So, "previous sample" (in the context of LTspice computation) makes little sense.


If you do want to evaluate in terms of a sampled data system, then you need to add a sample "clock" to your circuit and a sample/hold to the circuit. Then, process the S/H output.


Jim Wagner
Oregon Research Electronics

feabyl wrote:

How to implement an expression D(t)=D(t-1)+ a ?

Is that D(t-1) as in D(t - 1sec)?

If so, you can implement a 1 second time delay in either of two ways:

1. A (properly terminated) lossless transmission line (T-element) with a
delay of 1 second.

2. A behavioral source (B-element) with a delay of 1 second.

If the '-1' is supposed to represent the previous internal timestep in
LTspice, I don't think there is a way to do that. (But I'm not saying it
is impossible.)

Regards,
Andy

(PS: I'm not quite sure what you are trying to achieve with that
expression, but I hope you know what you are doing there.)

alzie wrote:

Ohms law says that your current is over 20A

Quite a lot for a little TVS.
Theyre usually meant for short spikes.

20A * 36V = 720W
That would convert youre TVS into a SED in short order.
(smoke emitting device)

You may need to use a real SCR crow bar and a fuse to be safe.

The TVS may be sufficient. Like you say, they are meant to handle short
spikes, and that might be all that it ever sees ... ignition noise and
such. The instantaneous power could be up there but it's not wide enough
to heat up the device. The simulated waveform is probably very pessimistic.

Andy

Hi eqmqiq


On 07/10/2013 01:44 AM, eqmqiq wrote:

Thanks for everyone's suggestion, I put a new TVS from the LTspice
library(SMBJ24CA) and set a series resistance(0.5 ohm) for the voltage
source.
the simulation result shows the voltage is clamped at 36V, but the
breakdown voltage of the TVS is 24V, I don't understand why...? wrong
parameter setting??
I update the asc file to TEMP folder with the same file name "
TVS_clamp.asc"

Ohms law says that your current is over 20A
Quite a lot for a little TVS.
Theyre usually meant for short spikes.

20A * 36V = 720W
That would convert youre TVS into a SED in short order.
(smoke emitting device)

You may need to use a real SCR crow bar and a fuse to be safe.


--


AC2CL

I do not think there is any thrill that
can go through the human heart like that felt by the inventor as
he sees some creation of the brain unfolding to success...
Such emotions make a man forget food, sleep, friends, love, everything.

- Nikola Tesla

--- In LTspice@..., "suri_bright" <nghoang_98@...> wrote:

Hi all, I would like to create the integrate and dump in LTspice
(the same with integrate and dump block in Matlab). I can create
the integrate by the equivalent idt() with bv.asv. However, I do
not know how to dump the signal. Is there any one know how to do
please help? Thanks

Yes, I do, but please go - go to where you may find the knowledge
of ALL the yummy, delicious brains forever preserved for your
eternal consumption in the great secret brain lockers known as
the group Message Archive and the Magical Help File. The key
password you will need is... "idt reset".

Now, go, go away. Begone o' Zombie.

PS: There are those who claim that homework zombieism may be cured
through much personal initiative, hard work and the willingness to
actually experiment with the brain-ware (i.e., LTspice). Yum!

The invasion has begun... "Uhg-uhg. Brains, I need brains [drool]"

Look at the line that starts the definition of the subcircuit.
?
?
.SUBCKT 06HPR33 1 2 3

You will notice that the subcircuit has 3 external nodes (1 2 3). The native inductor has only two external nodes. You cannot use the inductor symbol and assign this subcircuit to it because of the node mismatch. If you look in the Files section of this group,
?
Files > Tut > S-Parameter > S-Parameter to SPICE
you will find a symbol file for a 2-port device (S2PORT.asy). Your s-parameter file is a 2-port file as designated by the extension .s2p. You will notice that the 2-port symbol has three external nodes. Two of them connect to the nodes in your circuit where you would connect the inductor. The third node is ground.
?
?

________________________________
From: ayman_hendawy <ayman_hendawy@...>
To: LTspice@...
Sent: Wednesday, July 10, 2013 6:50 AM
Subject: [LTspice] import Touchstone file (s2p) to LTSpice

?
Hi,

I have ".s2p" files of some inductors and I need to import this file as a model to the inductors I have drawn in LTSpice in order to use it in the simulation, in order to do a practical simulation.

I downloaded the "s2spice_097.exe" from the "group files" and generate the .lib file, I get a file like this:
/***/
.SUBCKT 06HPR33 1 2 3
* MHz S MA R 50
* Z1=50.000000 Z2=50.000000

R1N 1 10 -5.000000e+001
R1P 10 11 1.000000e+002
R2N 2 20 -5.000000e+001
R2P 20 21 1.000000e+002

*S11 FREQ MAG PHASE
E11 11 12 FREQ {V(10,3)}= MAG
+( 1.000000e+006, 4.400000e-002, 2.585500e+001)
+( 1.047000e+006, 4.400000e-002, 2.681900e+001)
+( 1.097000e+006, 4.500000e-002, 2.780500e+001)
.
.
.
/**/

Then I added to my inductor in the spicemodel field: 06HPR33 , and add in the spice directive the following: .lib "the path to my .lib file".

But when I run the simulation I get nothing for the inductor, so kindly advice what I'm doing wrong.

Thanks