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Is this an error? I just started using LTspice and I'm trying to use a circuit with an LT1210 and it shows two + supply inputs instead of the usual + and - supply inputs. Thanks gentlemen.

In message <k1giju+bb95@...>, dated Mon, 27 Aug 2012, ridethesnake7miles <ridethesnake7miles@...> writes:

I'm trying to figure out how to model a standard No. 47 flashlight lamp. I'm having trouble trying to find a similar model. Oh yeah, I'm new to this software.

You should learn to search the archive files on the list's web site. See, for example:

0message%20number/msg%203491/
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
Instead of saying that the government is doing too little, too late or too
much, too early, say they've got is exactly right, thus throwing them into
total confusion.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Hi Helmut,

as always, I am deeply appreciative of this group, of your moderation and assistance, and to LT for making it free.

having said all that, I have noticed one thing that I don't think is directly my fault in being a most NON-expert user of LTspice: when I use an outside .asy and .subckt, it sure seems to me that I get a lot more run errors of all kinds.

For example, I had to give up on using TI's TL081 op amp symbol and model, because LTspice kept insisting - but in an oddly random fashion; it wasn't every time - there was a floating node. I examined the .asy in great detail; I examined the .subckt in great detail; I examined the circuit connections in exhaustive detail; nowhere could I find any hint of why LTspice was rejecting the .asy or the .subckt, but I eventually just had to give up and use the "universal op amp" symbol and LTspice's built-in model for it. I would have used an LT op amp, but it was extremely difficult for me to figure out which LT op amp was comparable to the TL081; I eventually gave up on that as well, despite searching over and over again through the LT website (without the help of a cross-reference, of course).

So, it's weird...on the one hand, LTspice is free, this group is free, and why should I complain? I am not complaining. It's just that if I could get a spice that worked really well with a good user interface for $250, where I could use all the devices out there without huge hassle, I would switch in a heartbeat.

I almost went for Beige Bag's spice, but there were too many downsides to it. I am going to look for the "optimizer" you mention; I would gladly pay $45 for anything that would make using LTspice easier.

VB, Maturin

Hi Tom.

tomshong wrote:

Thanks. I ran the simulation a few times times over the weekend, and I got more questions...

1) Why was the carrier signal set as 1 megahertz? That's not in the AM band.

Just d/loaded your schematic.

Edited Simulation command.
Removed .op analysis
Added transient to run for 1ms (first and only parameter).

Pretty wave form. :-)

Half a megahertz is. Probably just for convenience since it does have to handle 550 KHz or thereabouts.

2) Looking at the Transient Response

Looking at the output of the Darlington Pair at the collector of Q2, it seems it clipped the top half of the modulated signal. How did that happen? With a VDC of 9v there should be plenty of head room for the signal to swing up?

If Q2 goes low, Q1 turns off so that Q2 turns on again which tends to turn Q1 on again so they arrive at a compromise at 1.2 V at Q1's emitter.

Q2 is therefore running at its turn-on threshold so it doesn't amplify the signal below the average level as much as it does the signal that is above it. Note that this transistor is very nearly saturated as well and that's the bias voltage for Q1.

3) On the more fundamental level why Darlington pair? That is, why do we need to have a current gain at this stage?

It's not really a darlington. Or... well, it's more than that. The first transistor is a voltage follower and also the first stage of an inverting amp, which requires the second transistor in order to shift the voltage levels to a point where they can fall below Q1's emitter (and thus shut off Q1, which can't be done in a single stage).

4) How does the Q3, a Common Emitter with a feedback, work as a demodulator?

Non-linear amplification.

5) Looking at the AC response.
Following what I observed from the transient response, somehow I was expecting to see a filtered out frequency response of only the audio signal at the output. Yet, it look like whatever resonant frequency between L and C and antenna is carried over to Q3 output and didn't get filtered out. Can someone explain what is going on here?

Q3's base does get the half-cleaned up signal. All it needs to do is to filter out the high frequency to get the sine wave out.

The impedance of Q3's collector is set by the 10K resistor (if it was not connected to anything following that point). C5 passes both audio and carrier to the output which is also terminated by 10K making the impedance about 5K for the mixed signals at C5 which is 2.2nF.

The rolloff frequency for 5K and 2.2nF is 1 / (about 6 times R x C plus tax =) aboutt 15KHz.

C5 is where the signal becomes audio.

VTL5C4/2 and VTL5C3/2 - OPTOCOUPLER models needed.
Thank you

I'm trying to figure out how to model a standard No. 47 flashlight lamp. I'm having trouble trying to find a similar model. Oh yeah, I'm new to this software.

1MHz IS in the AM band. 1MHz = 1000KHz. The AM band in the North America goes from 531KHz to 1881KHz, That puts 1MHz right in the middle. In some parts of the world, this is referred to as the "MW" (Medium Wave) band.


Jim Wagner
Oregon Research Electronics

Will get the latest version and recheck. I was using 4.15r.

Thanks.

Helmut wrote:

This file:
RS/my-circuits/lp339_lp2901.asc
found here


Is a schematic from TI but the default transistors (copied from the examples/Educational/NE555.asc file couldn't pull the output up so I cut and jumpered one transistor to Vcc.

I messed with the few parameters to attempt to model a smaller transistor geometry but that didn't work.

Anyway, the schematic is accurate and interesting, but there may be one error in it and if anyone can correct that without monkeying with the current sources, it would be much appreciated.

Thanks.

Thanks. I ran the simulation a few times times over the weekend, and I got more questions...

1) Why was the carrier signal set as 1 megahertz? That's not in the AM band.

2) Looking at the Transient Response

Looking at the output of the Darlington Pair at the collector of Q2, it seems it clipped the top half of the modulated signal. How did that happen? With a VDC of 9v there should be plenty of head room for the signal to swing up?

3) On the more fundamental level… why Darlington pair? That is, why do we need to have a current gain at this stage?

4) How does the Q3, a Common Emitter with a feedback, work as a demodulator?

5) Looking at the AC response.
Following what I observed from the transient response, somehow I was expecting to see a filtered out frequency response of only the audio signal at the output. Yet, it look like whatever resonant frequency between L and C and antenna is carried over to Q3 output and didn't get filtered out. Can someone explain what is going on here?

--- In LTspice@..., rainbowsally <rainbowsally@...> wrote:

The .four or .fourier spice directive using the syntax in the docs does
not appear to work correctly.

When I create a net label named "OUT" and set the directive like so:
".fourier 1k v(out)"
ltspice says it can't find v(a) for the fourier analysis of THD. If I
then add a net label 'A' along side of 'OUT', it then computes the THD
correctly for node A but issues an error:

--> .fourier quantity "V(out)" not pressent in data.

If I remove the v(out) from the .fourier directive like so:
".fourier 1k"

It then works perfectly with the net label it appears to demand.

Either the docs are wrong or the program is broken.

Incidentally my third hack at kevin's amp at 100 W is Total Harmonic
Distortion: 0.052534% if we can believe that. But the components are not
final ones because I haven't yet looked at power issues with the ones used.

Also d/loaded texas instrument's tina. I like ltspice better though
tina is prettier and has a few features like 'temperature' testing that
are missing in ltspice. But tina apparently can't do THD calculations
at all.

To test THD for an amp the workaround in ltspice is as follows.

Add a spice directive (edit->text) ".four 1khz" (typically) and run the
transient analysis. Type 'ctrl-l' to view the log and scroll down to
the bottom of the fourier series to see the THD.

Works great! ...I think. Only checked one amp so far tho.

Hello,
I just tested the FOUR command. It has worked without problems.
I am sure you did something wrong in your schematic. I used
version 4.15s of LTspice.

.FOUR 1k V(OUT)

If you still have problems, then upload your schematic.
I will then check it.

Best regards,
Helmut

The .four or .fourier spice directive using the syntax in the docs does not appear to work correctly.

When I create a net label named "OUT" and set the directive like so:
".fourier 1k v(out)"
ltspice says it can't find v(a) for the fourier analysis of THD. If I then add a net label 'A' along side of 'OUT', it then computes the THD correctly for node A but issues an error:

--> .fourier quantity "V(out)" not pressent in data.

If I remove the v(out) from the .fourier directive like so:
".fourier 1k"

It then works perfectly with the net label it appears to demand.

Either the docs are wrong or the program is broken.

Incidentally my third hack at kevin's amp at 100 W is Total Harmonic Distortion: 0.052534% if we can believe that. But the components are not final ones because I haven't yet looked at power issues with the ones used.

Also d/loaded texas instrument's tina. I like ltspice better though tina is prettier and has a few features like 'temperature' testing that are missing in ltspice. But tina apparently can't do THD calculations at all.

To test THD for an amp the workaround in ltspice is as follows.

Add a spice directive (edit->text) ".four 1khz" (typically) and run the transient analysis. Type 'ctrl-l' to view the log and scroll down to the bottom of the fourier series to see the THD.

Works great! ...I think. Only checked one amp so far tho.

--- In LTspice@..., "sawreyrw" <sawreyrw@...> wrote:

--- In LTspice@..., "legendary_earl_e_bird" <m-marcus@> wrote:

Hello everyone,

I have a problem with ac analysis of my circuit (can be found in Files > Temp > AC Analysis > TEC-Model.asc). The overall circuit consists of two separate circuits which are connected with each other by behaviourale sources. Transient analysis seems to work flawlessly as expected, however ac analysis doesn't unfortunately. My goal is to get the transfer function of this particular circuit with input being voltage (net name = V_input) and output being temperature (net name = T_h_TC).
To begin with I had tried the laborious way of manually determining the bode diagram by performing transient analysis at several frequencies (0.001 0.01 0.1 1)Hz with sinusoidal excitation. I then compared amplitudes and phases of input and output at each frequency to get the bode plots of my system. It works but the process takes up too much time...
All I want is to apply a ac sweep from 0.001 to 1 Hz on my system to see how the output responds, however, the output is steady with absolut no changes when doing so (as a matter of fact, there are no changes anywhere within the circuit). It seems as the output is not dependent on the input anymore when performing ac analysis and I was wondering for quite a while now why that is the case? I suspect that the behaviourale sources are the cause for this phenomenon as they connect input and output.
I was hoping an LTspice expert could help me with this issue?

Many thanks in advance already.

Hello,

.AC analysis is a small signal AC analysis. This means that the model is linearized at the DC operating point before the AC sweep is done. If you model contains BV sources of the form V=V(a)*V(b) and the DC value of either V(a) or V(b) is zero, the output of the small signal model will be zero. This is not a problem with SPICE; it is the way the math works. Your i(R_m1) terms are probably causing the result you are getting.

Rick

Hello Rick,
Thanks for pointing to the mistake.
I have uploaded the same circuit using an additional V-source
to solve the problem. It's common in SPICE to use a V-source
with 0V for current measurement.

Files > Temp > TEC-Model1.asc

Best regards,
Helmut

As an alternative electronics group for discussion of all things audio,
head over to www.diyaudio.com. You can bat around ideas with Nelson
Pass, Bob Cordell, John Curl and many other notable audio designers.
Spice simulation is tolerated there as well but most believe in actually
building the circuit and measuring it.

I can understand what you're saying, but not why you are quoting me.


Vlad

Does the company LT spice intends to make upgrade on LTSpice to improve useability?

In case it wasn't clear already ...

This forum is essentially a user's group, a collection of LTspice
users. It is not run by Linear Technology Corporation (LTC)
(www.linear.com), and is not even moderated by them. Yes there is at
least one employee of Linear who visits here often, but he (Mike) is
not a moderator here. We are LTspice users, not LTspice program
developers.

I think the person to direct this question to, is Mike; and/or the
management of Linear Technology, the company behind LTspice. The
other 38,000 people here don't work for Linear and have no direct say
in the program's development.

However, my personal view is that LTspice is, and has continually been
improved. and I expect that this trend will likely continue. But I
don't speak for the management of LTC.

If you don't think LTspice has improved over the years, then you may
have a very narrow view of what features it needs, only to suit your
specific requirements. LTspice has a wide user base and its features
have expanded to meet the needs of that user base. It handles
3rd-party SPICE models (non-Linear Tech products) very well and I
would guess that the vast majority of users are using it with
3rd-party models. (Yes there are exceptions; encrypted HSpice models
are an example of that.) I would not expect LTspice to ship complete
with non-LTC SPICE models built-in to the program or in its libraries.

Are you looking for a statement from their Board of Directors, saying
that they intend to continue development of and improvements to the
program?

Andy

As an alternative electronics group for discussion of all things audio,
head over to www.diyaudio.com. You can bat around ideas with Nelson
Pass, Bob Cordell, John Curl and many other notable audio designers.
Spice simulation is tolerated there as well but most believe in actually
building the circuit and measuring it.

--- In LTspice@..., "legendary_earl_e_bird" <m-marcus@...> wrote:

Hello everyone,

I have a problem with ac analysis of my circuit (can be found in Files > Temp > AC Analysis > TEC-Model.asc). The overall circuit consists of two separate circuits which are connected with each other by behaviourale sources. Transient analysis seems to work flawlessly as expected, however ac analysis doesn't unfortunately. My goal is to get the transfer function of this particular circuit with input being voltage (net name = V_input) and output being temperature (net name = T_h_TC).
To begin with I had tried the laborious way of manually determining the bode diagram by performing transient analysis at several frequencies (0.001 0.01 0.1 1)Hz with sinusoidal excitation. I then compared amplitudes and phases of input and output at each frequency to get the bode plots of my system. It works but the process takes up too much time...
All I want is to apply a ac sweep from 0.001 to 1 Hz on my system to see how the output responds, however, the output is steady with absolut no changes when doing so (as a matter of fact, there are no changes anywhere within the circuit). It seems as the output is not dependent on the input anymore when performing ac analysis and I was wondering for quite a while now why that is the case? I suspect that the behaviourale sources are the cause for this phenomenon as they connect input and output.
I was hoping an LTspice expert could help me with this issue?

Many thanks in advance already.

Hello,

.AC analysis is a small signal AC analysis. This means that the model is linearized at the DC operating point before the AC sweep is done. If you model contains BV sources of the form V=V(a)*V(b) and the DC value of either V(a) or V(b) is zero, the output of the small signal model will be zero. This is not a problem with SPICE; it is the way the math works. Your i(R_m1) terms are probably causing the result you are getting.

Rick

Hello everyone,

I have a problem with ac analysis of my circuit (can be found in Files > Temp > AC Analysis > TEC-Model.asc). The overall circuit consists of two separate circuits which are connected with each other by behaviourale sources. Transient analysis seems to work flawlessly as expected, however ac analysis doesn't unfortunately. My goal is to get the transfer function of this particular circuit with input being voltage (net name = V_input) and output being temperature (net name = T_h_TC).
To begin with I had tried the laborious way of manually determining the bode diagram by performing transient analysis at several frequencies (0.001 0.01 0.1 1)Hz with sinusoidal excitation. I then compared amplitudes and phases of input and output at each frequency to get the bode plots of my system. It works but the process takes up too much time...
All I want is to apply a ac sweep from 0.001 to 1 Hz on my system to see how the output responds, however, the output is steady with absolut no changes when doing so (as a matter of fact, there are no changes anywhere within the circuit). It seems as the output is not dependent on the input anymore when performing ac analysis and I was wondering for quite a while now why that is the case? I suspect that the behaviourale sources are the cause for this phenomenon as they connect input and output.
I was hoping an LTspice expert could help me with this issue?

Many thanks in advance already.

--- In LTspice@..., "ciidcao@..." <ciidcao@...> wrote:

got 300+ emails for two days...

As few as that:-)

--- In LTspice@..., "jtanalog" <ltlist@> wrote:

I don't know if the LTspice List has been hacked but I'm suddenly barraged with spam, like ~100 E-mails per day... sent to an address I use only for LTspice. So I changed my address. (Easy for me, I maintain ~200 different E-mail addresses just to cope with such situations :-)

Seriously I note from the Yahoo Group Managers Forum



(you can all drop by, the messages are open to any one to read)

that recent Yahoo problems whereby many folks could not post, upload photos, or add members to groups by the web interface have been have been attributed to flaws with its "defensive" software that I guess, stops among other things "spam submissions", "guessing on passwords" and "bot networks" from creating dummy ids, making multiple postings and harvesting e-mails etc.

Perhaps another side effect was that in order to fix the problems they had to lower the defenses for a while hence the bursts of spam.

Dave
G4UGM

PS If any one thinks this is a fairy story, then I'll happily discuss off list. From time to time I have to look at the fire wall logs for a small UK town council. (My employer). If we are deemed worthy of attack I can't conceive the onslaught that must be thrown at Yahoo.

In message <k1f6b3+f6lm@...>, dated Mon, 27 Aug 2012, Richard <riscy00@...> writes:

###Sorry I should make myself clear, I was referring to independent Y-axis scale of 2,3,4 type, ie one y-axis -1V to +1V and other y-axis -50V to +10V and so on. When doing noise/interference analysis, one axis show uV scale while the PSU O/P with ripple on V scale.

You can use waveform arithmetic to do that. To plot a microvolt value Vu with tens-of-volt values, click on 'Vu' at the top of the plot and enter 'Vu*1E7' in the dialogue box.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
Instead of saying that the government is doing too little, too late or too
much, too early, say they've got is exactly right, thus throwing them into
total confusion.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK