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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
Re: plotting gm_over_Id vs IC for MOS transistor

 

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?
Thanks.
Re: Oscillator based on a multiple-feedback filter

 

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That's the one. Thanks, Tony.

On 2025-04-13 14:50, Tony Casey via groups.io wrote:
You might be referring to: MFB_Oscillator.zip. It came up in discussions here recently, but I originally uploaded it in 2022. Please use it as a basis rather than a blueprint.

--
Regards,
Tony

On 13/04/2025 15:38, John Woodgate via groups.io wrote:
Did someone upload such a circuit earlier this year? I saved, wherever it came from, but now I can't find it.

--
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: AC Analysis - show Mag in dBuV versus Freuqncy

 

Add a voltage dependent voltage source to the output node and multiply it by 1meg.?
Re: Oscillator based on a multiple-feedback filter

 

开云体育

You might be referring to: MFB_Oscillator.zip. It came up in discussions here recently, but I originally uploaded it in 2022. Please use it as a basis rather than a blueprint.

--
Regards,
Tony

On 13/04/2025 15:38, John Woodgate via groups.io wrote:

Did someone upload such a circuit earlier this year? I saved, wherever it came from, but now I can't find it.
Oscillator based on a multiple-feedback filter

 

开云体育

Did someone upload such a circuit earlier this year? I saved, wherever it came from, but now I can't find it.

--
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: AC Analysis - show Mag in dBuV versus Freuqncy

 

Modify your source for an amplitude of 1u.All measurements will be referred to 1uV.
Re: AC Analysis - show Mag in dBuV versus Freuqncy

 

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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 groups.io 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: AC Analysis - show Mag in dBuV versus Freuqncy

 

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.
Re: AC Analysis - show Mag in dBuV versus Freuqncy

 

开云体育

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 groups.io 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.
Re: AC Analysis - show Mag in dBuV versus Freuqncy

 

Hello, Ray


? ? I know of no? other way then to just right click on the traces label and include a conversion equation in the expression box.

Others may know better.


On Sat, Apr 12, 2025 at 5:08 PM, Ray. Koo via groups.io
<raymond.koosha@...> 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
AC Analysis - show Mag in dBuV versus Freuqncy

 

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
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