Simulation runs very slowly: test.asc
Hi All, ? ??????????????? In the uploaded file test.asc, I¡¯m having a problem with a simulation getting stuck. Would appreciate a look. ? Thanks, Chris
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Re: Good settings for RIAA square wave
I've learned there's two anti-RIAA filters you put at the input of preamp to be simulated: the laplace on and and RC passive one. All my sims with RIAA premps have the passive filter at the input, where I feed the AC signal through. According to one of my colleagues at DIYaaudio, "Laplace is the most accurate but can only be used in the .AC mode. For the .Tran mode you will have to use the RC model. As you mentioned on the use of Square Waves: you can tell quite a lot about even an audio circuit's performance, by looking at its square wave response. Tilt in the flat tops or ringing on the edges tells you that something is amiss with the low frequency or high frequency response, respectively. It's a quick-and-dirty way to judge the broadband response. That's what ignited my curiosity, and the recent tests with square waves and a scope in an actual built preamp on the thread by one of our pals. I did try some of the SW settings that you suggested, and for now found different responses according to the opamp being used. Now I need someone to translate those results into actual distortions or limits, and if possible play with the variables. On power amps, SW testing helped trim the parallel small caps on the feedback, which later showed as distortion changes in THD sims. This is the passive Jung filter I use on all my RIAA sims. (Lipshitz_and_Jung_1980)_RUS.png Carlos On Sun, Mar 30, 2025 at 1:21?AM Andy I via groups.io <AI.egrps+io@...> wrote:
RIAA is intended for audio applications. Why in the world would you even think of square wave input?
Actually, you can tell quite a lot about even an audio circuit's performance, by looking at its square wave response. Tilt in the flat tops or ringing on the edges tells you that something is amiss with the low frequency or high frequency response, respectively. It's a quick-and-dirty way to judge the broadband response.
That is, of course, assuming that you include an accurate inverse RIAA network. Without that, it would be meaningless and pointless.
Andy
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Hi,
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i have been interested in bipolar NDR devices similar to the Lambda-Diode and did some basic simulations which i can share later, if there is interest.?
I can also recommend the publications by Chua, where he identifies dozens of these circuits:
Negative resistance devices
Negative resistance devices: Part II
Bipolar - JFET - MOSFET negative resistance devices
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For now, try this link:
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Best,
Nils
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On 28/03/2025 19:44, sebastian.herrera
via groups.io wrote:
I am trying to
simulate a circuit with negative conductance using transistors and
passive components. Does anyone have a circuit for this?
A constant power load is an example of a circuit with negative
resistance. A common example of a constant power load is a
switch-mode converter. Quite a few SMPS designers don't appreciate
this.
Try this introduction:
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Regards,
Tony
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The circuit referenced in this note does have the advantage of using only NPN transistors and no zener. ?However, the I/V curve is less well defined and you have less control over the peak/valley voltages and currents. Otherwise, part count is similar.
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On "my" circuit, since zeners close to 5.5V are almost ideal and have very sharp knees, using one of those puts the peak voltage close to 5.5V; that may be a bit high for many applications. This circuit is very close to piecewise-linear so it is relatively easy to analyze with some precision. ?Some of the behavior DOES depend pretty strongly on the beta of Q1, however; for many transistors, beta can vary over a rather wide range.
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Jim
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On 03/29/2025 10:09 PM PDT alan victor via groups.io <avictor73@...> wrote:
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Along a similar line, this circuit placed in LTspice, provides negative conductance.?
Generate a single DC source sweep on applied V and monitor source current.?
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https://hackaday.com/2019/05/08/fun-with-negative-resistance-jellybean-transistors/#more-356020
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Along a similar line, this circuit placed in LTspice, provides negative conductance.?
Generate a single DC source sweep on applied V and monitor source current.?
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https://hackaday.com/2019/05/08/fun-with-negative-resistance-jellybean-transistors/#more-356020
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Re: Good settings for RIAA square wave
?
RIAA is intended for audio applications. ?Why in the world would you even think of square wave input?
Actually, you can tell quite a lot about even an audio circuit's performance, by looking at its square wave response.? Tilt in the flat tops or ringing on the edges tells you that something is amiss with the low frequency or high frequency response, respectively.? It's a quick-and-dirty way to judge the broadband response.
?
That is, of course, assuming that you include an accurate inverse RIAA network.? Without that, it would be meaningless and pointless.
?
Andy
?
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Re: Beginner's Question re LT Spice and RF Filter Design
Andy,
I saw that.? Am going through advisories and FAQ? - currently the basic beginner's tutorial- and come up to speed with any and all of relevance.
Appreciate the leg up!
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Good settings for RIAA square wave
RIAA is intended for audio applications. ?Why in the world would you even think of square wave input? OK, transient over-load behavior might be one reason, but I think that the OP is a long ways from that, yet.
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Jim Wagner
Oregon Research Electronics
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On 03/28/2025 9:32 AM PDT Carlos E. Mart¨ªnez via groups.io <carlo.mar.ll@...> wrote:
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Hi,
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This should be the first time I will be using a SW to test a RIAA preamp response.
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I was thinking of copying the settings I use for testing power amps, but I am not sure it's correct.
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They are: PULSE(-.4 .4 0 10n 10n 25u 50u 10)
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Would they be fine for this new test?
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Thanks!
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Carlos
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I think I have the circuit you need. It is circa-1965 and uses 3-4 bipolar transistors, a zener diode, and a handful of resistors. All components are "garden variety" with nothing special. It works to a few MHz. It IS a 2-terminal device and can be used much like a tunnel diode. Voltages are a lot higher than a tunnel diode: peak voltage is around 2V, valley voltage is around 5V and peak current is a few 10s of mA; all of these values are settable as part of the circuit design. ?I have it ONLY as a PDF but it is simple enough to create in LTspice. I will put it, appropriately named, in the group image/picture directory and post a message with a link. This should be done within a few hours of this message time.
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Jim Wagner
Oregon Research Electronics
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On 03/28/2025 11:44 AM PDT sebastian.herrera via groups.io <sebastian.herrera@...> wrote:
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Dear all, I am trying to simulate a circuit with negative conductance using transistors and passive components. Does anyone have a circuit for this?
Best regards.
Sebastian?
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Re: Beginner's Question re LT Spice and RF Filter Design
Andy,
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Thank you. I was to have uploaded the .asc file into temp per the group protocol but your answer will suffice. Appreciate the advisory and support.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Beginner's Question re LT Spice and RF Filter Design
I uploaded your schematic file.? It is "RF_Filter_Chebyshev.asc" and it is currently in the Temp folder, in the group's Files section. ?
Andy
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Re: Beginner's Question re LT Spice and RF Filter Design
Andy,
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I did so instinctively and THEN read the group webpage. My apologies for the oversight.
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--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Beginner's Question re LT Spice and RF Filter Design
On Sat, Mar 29, 2025 at 08:48 PM, k6whp wrote:
I note that the display shows this model to initially be -6dB and wonder why.
It's a pretty simple reason, which looks obvious after you realize it.
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Your signal source has a 1 (volt) amplitude and 50 ohm source impedance.? It is a Thevenin source, so you've got 1 volt behind the 50 ohm source resistance.? When that is terminated (into a 50 ohm load), it is a voltage divider that cuts the voltage in half, so that the terminal voltage across V1 is 0.5 volt, resulting in a nominal 6 dB loss.
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When using AC sources like this, set their amplitude to 2 (volts), so that they make 1 (volt) when terminated.
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Andy
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Re: Beginner's Question re LT Spice and RF Filter Design
On Sat, Mar 29, 2025 at 08:48 PM, k6whp wrote:
Am designing a low pass filter for the 20m amateur band, code below. (My apologies if this violates group protocol. Advise and I will adhere in the future.)?
Even better:? Why not read the group's guidelines on the main group webpage.
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You attempted to paste your schematic file into the message.? Never paste or attach any files into a group message.
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Andy
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Beginner's Question re LT Spice and RF Filter Design
Am designing a low pass filter for the 20m amateur band, code below. (My apologies if this violates group protocol. Advise and I will adhere in the future.)?
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I note that the display shows this model to initially be -6dB and wonder why. Again, truly a beginner. Links to appropriate material gratefully received.
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Thank you in advance.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
?
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Re: Simulating Using PyLTSpice Takes Too Long
Simply use six instances of your circuit on single page and modify connection\termination for each individual circuits.
Yes, it`s not elegant, but works as simple as hammer.
Not sure if some kind of "stepping" will work faster.
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Kind regards,
Victor
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Re: Simulating Using PyLTSpice Takes Too Long
On Sat, Mar 29, 2025 at 06:27 PM, <davitkharshiladze26@...> wrote:
I have made contact with PyLTspice developer, and he pointed out that It could not be sped up further.
I consider that an odd thing to say.
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On the one hand, it suggests that his program adds pre-programmed delays which can't be reduced further, without risk of failure.
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On the other hand, it suggests that he knows your circuit, and he's telling you it can't simulate faster.? How would be know that?? I think you were saying that the simulation itself (with just LTspice) is about 1 second (each time) and that 1 second is too slow.
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Andy
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Re: PTC model with internal temperature rise
On Sat, Mar 29, 2025 at 06:13 PM, <pilou@...> wrote:
It's OK now, I just uploaded it.
Filename is "ptc_sh.zip".
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It is currently in the Temp folder at the group's website. ?
Andy
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Tony Casey
k6whp
LV