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Re: Creating a dirt-simple subcircuit component

 

You cannot have a zero-ohm resistor in LTspice.? I've created a jumper with a 1f ohm resistance called MyJmpr.? The simple subcircuit is assigned it to the original jumper symbol and saved as MyJmpr.asy.? I have uploaded it to the Temp files as MyJmpr.zip.? I do like the idea of using a zero-volt voltage source.? You could do the same as I have done with the resistor and assign that as a subcircuit to the original jumper assembly and save the result as a new jumper.
John
?
Re: Creating a dirt-simple subcircuit component

 

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SO, no need to include the file name in the symbol Attributes editor?

?

From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Sunday, April 13, 2025 11:22 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

What "linkage"?

?

The filenames (minus the .ext) must match.? That's all the "linkage" you need.

?

Andy
Re: Creating a dirt-simple subcircuit component

 

No Prefix.
?
Andy
?
Re: Creating a dirt-simple subcircuit component

 

What "linkage"?
?
The filenames (minus the .ext) must match.? That's all the "linkage" you need.
?
Andy
Re: Creating a dirt-simple subcircuit component

 

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OK:

Erased prefix “X”

Have ZeroOhm OR ZeroOhm.asc in SpiceModel line

All works fine.

?

Thanks!

Dave

?

From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Sunday, April 13, 2025 11:11 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

Create the symbol from the schematic (.asc) file!

?

Must not have Prefix = X.

?

Andy

?
Re: Creating a dirt-simple subcircuit component

 

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I did.

Ah!? What prefix, then?

And still, where do I insert the linkage to ZeroOhm.asc?

?

From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Sunday, April 13, 2025 11:11 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

Create the symbol from the schematic (.asc) file!

?

Must not have Prefix = X.

?

Andy

?
Re: Creating a dirt-simple subcircuit component

 

Create the symbol from the schematic (.asc) file!
?
Must not have Prefix = X.
?
Andy
?
Re: AC Analysis - show Mag in dBuV versus Freuqncy

 

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If that weird design works for you, OK. This group doesn't do circuit design, but if you want to have a sensible low-pass filter, you could well use one of the filter design apps at

On 2025-04-13 18:52, Ray. Koo via groups.io wrote:
Hi John,
Please see my answer to items 1, 3, and 4.
1. The intention?was twofold, (a) to verify attention rate at -40dB/Dec and (b) to check filter behavior at higher frequencies
2. I could get???into the Vertical?Axis range but ltspice did not display it. That was an interesting suggestion.
3. Caps have esl = 10pH & 20pH, respectively.?
I re-run the simulation with esl and noticed the effect of stray inductances.
4. Yes, you are?correct there.

Very Best,
Ray

On Sun, Apr 13, 2025 at 1:09?AM John Woodgate via <jmw=[email protected]> wrote:

1. If you are only concerned with the response well below 1MHz, there is not much point in sweeping up to 10MHz.

2. You can't change the axis labels to dB?V within LTspice, but you can add text to the plot pane: 0dB = 1?V. With Windows, you can get ? with ALT+0181 on the numerical keypad, with NumLock enabled.

3. To see the effects of even small stray inductances, put 100nH in series with each capacitor. 24 dB gain at about 10 kHz, but see below about input impedance.

4. The input impedance [1V/I(L1)] is very low, less than 1 ohm up to 300 kHz and a minimum of 2 milliohms at about 10 kHz.

On 2025-04-13 02:10, Ray. Koo via wrote:
Hi John,

Thanks for your response.
fc of the first LC is 11.25kHz and that of the second?one is 32.83kHz which are << 1MHz.
I intend to show dBuV?instead of dB on the vertical axis of the Bode plot if that is doable with LTspice.

Thanks,
Ray

On Sat, Apr 12, 2025 at 3:18?PM John Woodgate via <jmw=[email protected]> wrote:

Right-click on V(out) at the top of the plot window and change it to V(out)/1u in the pane that opens. But that is never going to work properly, or as you expect, in practice, because those large capacitors resonate with internal and lead inductances, probably well below 1 MHz.

On 2025-04-12 22:07, Ray. Koo via wrote:
Hi LTspice Group,
?
I have simulated a filter which is a cascaded of two LC low-pass filters.
I get the Bode plot Magnitude in dB versus frequency and phase versus frequency.
?
However, I need to display the magnitude in dBuV versus frequency.
dB is just a value but dBuV is a value with reference 1uV.
I tried few things but no one worked.

Is there a way to show dBuV vs Frequency?
Has anyone tried it before?
?
LCLC filter is uploaded.
?
Comments are appreciated!
Ray
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion

Virus-free.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion
Re: Creating a dirt-simple subcircuit component

 

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I understood it to do exactly that, but it merges them in the netlist.

?

From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Sunday, April 13, 2025 10:47 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

The Jumper symbol is a confusing one, to me at least.? I do not usually see that it actually separates nodenames, but it may allow them.

?

Andy

?
Re: Creating a dirt-simple subcircuit component

 

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I agree, and have tried but can’t get it right!

I want to link the symbol to ZeroOhm.asc in the same folder.

Where/how to do that? In the symbol editor, Ctrl-A menu, right?

In the Spice Model line?

In the Value line?

With/out the “.asc”?

?

?

From: [email protected] <[email protected]> On Behalf Of Andy I via groups.io
Sent: Sunday, April 13, 2025 10:45 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

Where is the sUbcircuit?

?

I see a symbol, but not linked to any subcircuit.? That won't work.

?

NSY

?
Re: Creating a dirt-simple subcircuit component

 

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Yes, and I do that, but wanted a unique symbol and “true” zero in a single library device…

?

?

From: [email protected] <[email protected]> On Behalf Of John Woodgate
Sent: Sunday, April 13, 2025 10:48 AM
To: [email protected]
Subject: EXTERNAL: Re: [LTspice] Creating a dirt-simple subcircuit component

?

You haven't given your subcircuit any properties. Just writing 0 ohms on doesn't work. It's much simpler to put in an ordinary resistor and give it the value 1?ohm (r even 1pohm).

On 2025-04-13 18:27, Bell, Dave via groups.io wrote:

I am trying to make a better Jumper:

?

  1. The Lib Jumper does NOT separate net names (in VXVII, at least)
  2. I’m stupidly missing *something* in creating a new device

“Unknown subcircuit called in: xu1 a b”

?

Suggestions?

?

Thanks,

Dave

--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion

?

Virus-free.

Re: Creating a dirt-simple subcircuit component

 

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I agree it's 'better', insofar as it really has zero resistance, but it makes the .ASC look very odd, especially it it's to be given to a user of the physical circuit.

On 2025-04-13 18:51, Andy I via groups.io wrote:
On Sun, Apr 13, 2025 at 01:49 PM, John Woodgate wrote:

It's much simpler to put in an ordinary resistor and give it the value 1?ohm (r even 1pohm).

Or (better), a 0 V voltage source.
?
Andy
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion
Re: AC Analysis - show Mag in dBuV versus Freuqncy

 

Hi John,
Please see my answer to items 1, 3, and 4.
1. The intention?was twofold, (a) to verify attention rate at -40dB/Dec and (b) to check filter behavior at higher frequencies
2. I could get???into the Vertical?Axis range but ltspice did not display it. That was an interesting suggestion.
3. Caps have esl = 10pH & 20pH, respectively.?
I re-run the simulation with esl and noticed the effect of stray inductances.
4. Yes, you are?correct there.

Very Best,
Ray

On Sun, Apr 13, 2025 at 1:09?AM John Woodgate via <jmw=[email protected]> wrote:

1. If you are only concerned with the response well below 1MHz, there is not much point in sweeping up to 10MHz.

2. You can't change the axis labels to dB?V within LTspice, but you can add text to the plot pane: 0dB = 1?V. With Windows, you can get ? with ALT+0181 on the numerical keypad, with NumLock enabled.

3. To see the effects of even small stray inductances, put 100nH in series with each capacitor. 24 dB gain at about 10 kHz, but see below about input impedance.

4. The input impedance [1V/I(L1)] is very low, less than 1 ohm up to 300 kHz and a minimum of 2 milliohms at about 10 kHz.

On 2025-04-13 02:10, Ray. Koo via wrote:
Hi John,

Thanks for your response.
fc of the first LC is 11.25kHz and that of the second?one is 32.83kHz which are << 1MHz.
I intend to show dBuV?instead of dB on the vertical axis of the Bode plot if that is doable with LTspice.

Thanks,
Ray

On Sat, Apr 12, 2025 at 3:18?PM John Woodgate via <jmw=[email protected]> wrote:

Right-click on V(out) at the top of the plot window and change it to V(out)/1u in the pane that opens. But that is never going to work properly, or as you expect, in practice, because those large capacitors resonate with internal and lead inductances, probably well below 1 MHz.

On 2025-04-12 22:07, Ray. Koo via wrote:
Hi LTspice Group,
?
I have simulated a filter which is a cascaded of two LC low-pass filters.
I get the Bode plot Magnitude in dB versus frequency and phase versus frequency.
?
However, I need to display the magnitude in dBuV versus frequency.
dB is just a value but dBuV is a value with reference 1uV.
I tried few things but no one worked.

Is there a way to show dBuV vs Frequency?
Has anyone tried it before?
?
LCLC filter is uploaded.
?
Comments are appreciated!
Ray
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion

Virus-free.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion
Re: Creating a dirt-simple subcircuit component

 

On Sun, Apr 13, 2025 at 01:49 PM, John Woodgate wrote:

It's much simpler to put in an ordinary resistor and give it the value 1?ohm (r even 1pohm).

Or (better), a 0 V voltage source.
?
Andy

Re: Creating a dirt-simple subcircuit component

 

开云体育

You haven't given your subcircuit any properties. Just writing 0 ohms on doesn't work. It's much simpler to put in an ordinary resistor and give it the value 1?ohm (r even 1pohm).

On 2025-04-13 18:27, Bell, Dave via groups.io wrote:

I am trying to make a better Jumper:

?

  1. The Lib Jumper does NOT separate net names (in VXVII, at least)
  2. I’m stupidly missing *something* in creating a new device

“Unknown subcircuit called in: xu1 a b”

?

Suggestions?

?

Thanks,

Dave

--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only If something is true: * as far as we know - it's science *for certain - it's mathematics *unquestionably - it's religion

Virus-free.
Re: Creating a dirt-simple subcircuit component

 

The Jumper symbol is a confusing one, to me at least.? I do not usually see that it actually separates nodenames, but it may allow them.
?
Andy
?
Re: Creating a dirt-simple subcircuit component

 
Edited

Where is the sUbcircuit?
?
I see a symbol, but not linked to any subcircuit.? That won't work.
?
Andy
?
Creating a dirt-simple subcircuit component

 

开云体育

I am trying to make a better Jumper:

?

  1. The Lib Jumper does NOT separate net names (in VXVII, at least)
  2. I’m stupidly missing *something* in creating a new device

“Unknown subcircuit called in: xu1 a b”

?

Suggestions?

?

Thanks,

Dave
creating gm/Id vs Id/W plot in ltspice

 

Hello ,I have created a two plots of Id vs Vgs and? d(Id)/d(Vgs) [also known as gm] vs Vgs as shown in the attached link.
how can I create gm vs Id plot which unites the two?
Thanks.
?
?
/g/LTspice/files/Temp/2.zip
Re: plotting gm_over_Id vs IC for MOS transistor

 

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On 13/04/2025 16:42, john23 via groups.io wrote:
Hello, this is a very good thread I am trying to learn from.
However the links in the post are non functioning. Is there a way to know where are they now?
The links got broken when this group moved from Yahoo! to groups.io.

If you know the file or folder name from any of the links, you should be able to find it you go to Files and type in the name in the search box in the top right.

For example, for this link:

..you can search for "Transconductance Gm and Gds" and you will get one hit: the correct folder.

Notes:
  1. "%20" in any links should be replaced with a space.
  2. Include the quotation marks in the search terms because you're looking for the exact file or folder name.
--
Regards,
Tony
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