开云体育

Hi ppl,

I thought I would search for it - to test my abilities - I didn't find it.
I am learning a fair amount by just reading this group and others
troubles. So as my first reply to the group I will advice what I found on
a circuit site<>.
HIH - sorry if i am wrong - sounds like the guy knew what he was talking
about.

An optocoupler is just a current-controlled current source, pretty much,
close enough. That already exists. Maybe put a small capacitor across it to
simulate slowness.

(2nd post attempt - just to test it gets posted more then anything )
Thanks,
Colin




--
Thanks,
Colin

Hi Tom.

Try this.


File: AM_Receiver-rs-01.zip

What I changed.

Set VC to constant 100 pf so we can see what's going on and changed
R4 to a current source (using discretes).

Original:
Total Harmonic Distortion: about 17.5%

Modified:
Total Harmonic Distortion: 14%, 13% and half volume.

Not sure how it would work in the real world because it's also very
sensitive to C2 values. For example, if you double C2, the audio starts
out at lower amplitude (like an expander) but the THD goes down to about 5%.

Also to Jim. Thanks for the correction re. AM band.

The LP339 device is an open collector output and expects a resistor pull up to the positive rail.

this was a while ago, but you can modify it appropriately
from Jim Thompson

*VO=NOMINAL OPERATING VOLTAGE
*IO=NOMINAL STEADY STATE OPERATING CURRENT
*RCOLD=FILAMEMT RESISTANCE MEASURED AT ROOM TEMP (300K)
*TAU=CURRENT TIME CONSTANT AFTER A 0 (zero) TO VO STEP IS APPLIED
.SUBCKT LAMP 1 2 PARAMS: VO=28 IO=25m RCOLD=112 TAU=22m TAMB=300
H1 6 0 VML 1
RH1 6 0 1
GP 0 4 VALUE={V(6)*V(1,2)}
*V(4,0) = FILAMENT TEMPERATURE IN KELVINS
RT 4 5 {300*(VO-IO*RCOLD)/(IO*IO*VO*RCOLD)}
CT 4 5 {TAU*IO*IO*VO*RCOLD/(300*(VO-IO*RCOLD))}
VAMB 5 0 {TAMB}
El 7 0 1 2 300
R1 7 0 1
E2 8 0 VALUE={V(4)*RCOLD}
R2 8 0 1
E3 10 0 7 9 10MEG
R3 10 0 1
E4 9 0 VALUE={V(8)*V(10)}
R4 9 0 1
GR 1 3 10 2 1
VML 3 2 0
.ENDS LAMP


--- ridethesnake7miles@... wrote:

From: "ridethesnake7miles" <ridethesnake7miles@...>
To: LTspice@...
Subject: [LTspice] basic incandescent dc lamp
Date: Mon, 27 Aug 2012 19:42:54 -0000

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.

Hi ppl,

I thought I would search for it - to test my abilities - I didn't find it.
I am learning a fair amount by just reading this group and others
troubles.

So as my first reply to the group I will advice what I found on
a circuit site<>.
HIH - sorry if i am wrong - sounds like the guy knew what he was talking
about.

Thanks,
Colin

An optocoupler is just a current-controlled current source, pretty much,
close enough. That already exists. Maybe put a small capacitor across it to
simulate slowness.

On Mon, Aug 27, 2012 at 4:47 PM, bvebyz <bvebyz@...> wrote:

**


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

--
Thanks,
Colin



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

--- In LTspice@..., "Gandolf" <charlesknouse27@...> wrote:

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

Maturin,

I agree with Helmut on this one. I put all the relevant files you posted to the MATURIN TEMP folder into a common folder on my PC and the circuit ran fine except the LM139 model was not present. I deleted it and all the stuff around it, and the rest was fine.

As Helmut says, always put all you models in the same folder as your top level schematic. The is nothing wrong with LTspice, but it can't do anything about cockpit errors (except give a reasonable error message) or crappy models (except give a reasonable error message).

Rick

--- In LTspice@..., "afhockey623" <jxm1092@...> wrote:

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.

Hello,

Thanks for this report.
The power pin at the bottom should have a "-". I have reported now
this bug to Mike.

Please directly report this to LTC in the future, if you find
a bug. The email address is in the Help->About of the LTspice
program.

Best regards,
Helmut

In message <k1gmpk+qhts@...>, dated Mon, 27 Aug 2012, afhockey623 <jxm1092@...> writes:

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.

Yes; if you look at the data sheet, you can see it needs + and - supplies. You can report this to the email address given in the toolbar Help -> About drop-down.
--
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

On 27/08/2012 20:58, Gandolf wrote:

For example, I had to give up on using TI's TL081 op amp symbol and model,

I've been using TI's TL081 model without any problems but created my own symbol, just copied something else and renamed it.

Gordon
--

--- In LTspice@..., "afhockey623" <jxm1092@...> wrote:

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.

Hello,

Yes, the lower + terminal should be marked -. The models "test circuit" show a negative supply connected to that pin.

Rick

--- In LTspice@..., "Gandolf" <charlesknouse27@...> wrote:

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.

Hello,
I wonder what you did. My colleagues and I permanently use
models from LTC and other companies at the same time. They
have no problems with that except that some models hardly
converge, but this can happen with any SPICE simulator.
Most users who are in trouble with missing files had made
directory structures for their symbols and models instead
of just placing them in the folder of the schematic.

Many examples (symbols, models) are in the group's Files
especially in "Files > Libs".

...
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.

At some point I give up to convince somebody using LTspice.
It seems it's the case here.

Best regards,
Helmut

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.