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Re: I added a CD4007 model
Hello, The model DC characteristic may be ok, but? model with no capacitances is not reasonable.? You might be better off using LTspice logic devices. Rick On Saturday, December 7, 2013 6:46 PM, "davorslistdepot@..." wrote:
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Hi all,
I was missing a CD4007 model, so there it is. It is bare bones hierarchical model (so far) that I left that way so that it is easier to check what I did. If everything goes well, I'll make a subcircuit out of it. The transistors models are based on the 4007 library used at csupomona.edu, like this: .model NMOS NMOS LEVEL=2 VTo=1.4 Kp=.6m LAMBDA=0.005 .model PMOS PMOS LEVEL=2 VTo=-1.0 KP=.6m LAMBDA=0.01 No diodes or capacitances, and no resistors in this model. Just MOSFETs. Surprisingly this simple model produces a very nice Rds_on transfer plot, and triggers no alarms in error log. So far I'm happy with it. In CD4007L2_h.asc which is a hierarchy file i placed some comments about an easy way procedure of making a symbol out of a hierarchy, but please don't consider it a tutorial of any kind. |
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Re: I added a CD4007 model
Hello, The model DC characteristic may be ok, but? model with no capacitances is not reasonable.? You might be better off using LTspice logic devices. Rick On Saturday, December 7, 2013 6:46 PM, "davorslistdepot@..." wrote:
?
Hi all,
I was missing a CD4007 model, so there it is. It is bare bones hierarchical model (so far) that I left that way so that it is easier to check what I did. If everything goes well, I'll make a subcircuit out of it. The transistors models are based on the 4007 library used at csupomona.edu, like this: .model NMOS NMOS LEVEL=2 VTo=1.4 Kp=.6m LAMBDA=0.005 .model PMOS PMOS LEVEL=2 VTo=-1.0 KP=.6m LAMBDA=0.01 No diodes or capacitances, and no resistors in this model. Just MOSFETs. Surprisingly this simple model produces a very nice Rds_on transfer plot, and triggers no alarms in error log. So far I'm happy with it. In CD4007L2_h.asc which is a hierarchy file i placed some comments about an easy way procedure of making a symbol out of a hierarchy, but please don't consider it a tutorial of any kind. |
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Re: PWMs and Darlingtons
Ed, SPICE doesn't have built in signal source with a variable duty cycle.? It is easy to build one with a comparator where one input is a triangular waveform and the other is a control signal that causes the duty cycle to vary.? I have done this with BV source as the comparator.? Search the group files and messages for PWM demo. Rick On Saturday, December 7, 2013 6:36 PM, texasham10
wrote:
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I'm new to ltspice, and am trying to draw and simulate a circuit.
This includes a PWM output and a darlington transistor; I searched the libraries and downloaded a new bjt library, but it doesn't contain a TIP120 I also need a pointer to a "signal generator" square wave with a variable duty cycle. Any help? Ed |
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I added a CD4007 model
Hi all,
I was missing a CD4007 model, so there it is. It is bare bones hierarchical model (so far) that I left that way so that it is easier to check what I did. If everything goes well, I'll make a subcircuit out of it. The transistors models are based on the 4007 library used at csupomona.edu, like this: .model NMOS NMOS LEVEL=2 VTo=1.4 Kp=.6m LAMBDA=0.005 .model PMOS PMOS LEVEL=2 VTo=-1.0 KP=.6m LAMBDA=0.01 No diodes or capacitances, and no resistors in this model. Just MOSFETs. Surprisingly this simple model produces a very nice Rds_on transfer plot, and triggers no alarms in error log. So far I'm happy with it. In CD4007L2_h.asc which is a hierarchy file i placed some comments about an easy way procedure of making a symbol out of a hierarchy, but please don't consider it a tutorial of any kind. |
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PWMs and Darlingtons
texasham10
I'm new to ltspice, and am trying to draw and simulate a circuit.
This includes a PWM output and a darlington transistor; I searched the libraries and downloaded a new bjt library, but it doesn't contain a TIP120 I also need a pointer to a "signal generator" square wave with a variable duty cycle. Any help? Ed |
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Re: Questions about phase in .AC LTspice Analysis
¿ªÔÆÌåÓýLe 06/12/2013 16:28, Andy a ¨¦crit?:
?Thanks for this explanation. I just wonder why the OP included this statement. |
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Re: Questions about phase in .AC LTspice Analysis
¿ªÔÆÌåÓýLe 06/12/2013 09:24,
analogspiceman@... a ¨¦crit?:
?Just plain ignorance. I didn't know that. I can't find it in the Control Panel. Anyway I wonder why this would be an option... |
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Re: Determine phase and gain margin in filter/amp
Maarten, You set up the circuit correctly, but did you determine the phase margin by plotting V(fb)/V(inm)?? Doing this I see a phase margin of 72.8 degrees at 9.16 MHz.? In think the circuit is ok, but you should be aware that the output impedance of U2 has a significant effect.? You can see that V(ref) increases significantly as the frequency goes up. Rick |
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Re: CD4047 BC
VARDKES wrote: Does anyone have CD4047BC spice model? There are models for the CD4047B. ?I don't know if or how a *BC differs from a *B part. Re-read the directions on this group's main webpage. ?Find, download, and open the "Table of Contents" file, then search through that file for "CD4047". ?It comes up in a few different places. ?The links in the Table of Contents file are hot-links, so when you click on them, it should bring you to the online directory where the models are located.
Regards,
Andy |
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Re: xr2211 model
ignaciogouetv?wrote:
With enough ingenuity and guesswork, you can create a subcircuit for just about anything. ?The question is, how accurate is it?
A PLL is not always the easiest thing to start with, unless you know something about the actual chip design they used.
Fortunately, Exar's datasheet includes an "equivalent schematic diagram" towards the back, so you could replicate that in an LTspice schematic and turn it into a subcircuit. ?Keep in mind that such diagrams from manufacturers are approximate and may leave a lot out. ?Also we don't know the characteristics of the transistors and diodes, nor the sizes of all the current sources. ?But it's better than nothing.
There is a working subcircuit for the XR2206 (another PLL) in the "Files" section of this YahooGroup. ?You might consult that to see if it gives you anything you can use. ?If nothing else, it probably has the characteristics (.MODEL statements) of the diodes and transistors for a similar Exar IC (but I can't say how accurate that model is).
It is puzzling that Exar's own XR2211 datasheet is labeled Version 1.0.4 (or 1.04), but the copies found elsewhere on the 'net are version 3.01. ?Strange. ?They have the same date.
Regards,
Andy |
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Re: Questions about phase in .AC LTspice Analysis
Hello Hnguyen,
> Could you please tell me where they are, so that I can learn from that. Open your original "wrong" asc-file. Right-mouse-click on the symbol of the source "Vcmfb1_2c" and "Vcmfb2_2c". The V-source dialog window will pop-up. You will see a field "AC Amplitude". This should be empty or 0 in your simulation. You will also see that you have un-ticked "make this information visible on the schematic". AC Amplitude: 1 Best regards, Helmut |
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Re: Questions about phase in .AC LTspice Analysis
hoa van nguyen
Hallo Helmut, I found 2 extra AC sources in Vcmfb1/2 and It was an accident. Imaging how you found them. Thanks Hnguyen On , hoa van nguyen wrote: Hello Helmut & Andy, Thank you for helping me. Helmut: You
have defined "AC 1" in two extra sources. This is simply wrong for
this application. Instead you should define AC 1 in the input source. By
the way it's bad practice to hide the AC-value in a V-sources as you
did. A: it must be an accident. I ran your corrected "2stages_2CascodeDiff_ACsim_test2.asc"? and it works great, but I still don't see where are "AC 1" in two extra sources in my schematic. Could you please tell me where they are, so that I can learn from that. Now slowly I understand what you tell me. I need time to think about what I learn so far from your guys and would like to go back to your guys for my full understanding. Regards Hnguyen On Friday, December 6, 2013 12:48 PM, "helmutsennewald@..." wrote:
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Hello Hnguyen, You have defined "AC 1" in two extra sources. This is simply wrong for this application. Instead you should define AC 1 in the input source. By the way it's bad practice to hide the AC-value in a V-sources as you did. I have corrected your schematics and uploaded it into your folder. Simulate
with my files and you will see that everything is OK now. Best regards, Helmut
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Re: Questions about phase in .AC LTspice Analysis
hoa van nguyen
Hello Helmut & Andy, Thank you for helping me. Helmut: You have defined "AC 1" in two extra sources. This is simply wrong for
this application. Instead you should define AC 1 in the input source. By
the way it's bad practice to hide the AC-value in a V-sources as you
did. A: it must be an accident. I ran your corrected "2stages_2CascodeDiff_ACsim_test2.asc"? and it works great, but I still don't see where are "AC 1" in two extra sources in my schematic. Could you please tell me where they are, so that I can learn from that. Now slowly I understand what you tell me. I need time to think about what I learn so far from your guys and would like to go back to your guys for my full understanding. Regards Hnguyen On Friday, December 6, 2013 12:48 PM, "helmutsennewald@..." wrote:
?
Hello Hnguyen, You have defined "AC 1" in two extra sources. This is simply wrong for this application. Instead you should define AC 1 in the input source. By the way it's bad practice to hide the AC-value in a V-sources as you did. I have corrected your schematics and uploaded it into your folder. Simulate
with my files and you will see that everything is OK now. Best regards, Helmut
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Re: Questions about phase in .AC LTspice Analysis
Hello Hnguyen, You have defined "AC 1" in two extra sources. This is simply wrong for this application. Instead you should define AC 1 in the input source. By the way it's bad practice to hide the AC-value in a V-sources as you did. I have corrected your schematics and uploaded it into your folder. Simulate with my files and you will see that everything is OK now. Best regards, Helmut |
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Re: Questions about phase in .AC LTspice Analysis
hoa van nguyen
Hello Andy, Your thinking is what I see in "2stages_2CascodeDiff_ACsim_test1.jpg". Andy: I think the main reason is that those two bias sources have a large AC component (10 times the magnitude of the actual input signal). ?Why do you have input signals (AC components) entering through three different places into your amplifier circuit? ?I would think that should not be happening, which makes me believe your .AC simulation is not simulating the circuit you think it is. Do you mean 2 bias sources: Vcmfb1_2C_V & Vcmfb2_2C_V? let me explain what problem I have. These Vcmfb1_2C_V & Vcmfb2_2C_V are actually come from CMFB-Circuits (Common mode Feedback with switch capacitors, clocks) which adjust the common mode of outputs to Vdd/2: (Vodm+Vodp)/2 = Vdd/2 and (Vop+Vom)/2 = Vdd/2. Since the CMFB-Circuits only work in TRAN-Analysis, so I get these values Vcmfb1_2C_V & Vcmfb2_2C_V from TRAN-Analysis. So I use these 2 values for AC-Analysis. I didn't specify AC components for these 2 voltage sources, so I thought it should be alright. What should I do now? I see something wrong with my biasing!! Regards Hnguyen On Friday, December 6, 2013 7:29 AM, Andy wrote:
?
Jerry Lee Marcel wrote:
That's because of this statement on the schematic:
? .Save V(*) Comment it out and re-run, and you can plot currents. Andy |
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Re: CD4047 BC
Does anyone have CD4047BC spice model?
toggle quoted message
Show quoted text
--- In LTspice@..., shawn coleman <scolem26@...> wrote:
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Re: Determine phase and gain margin in filter/amp
Typically opamps will have low impedance follower type output stages so that open loop output impedance versus frequency remains low (20 to 50 ohms) to well beyond the opamp's gain-bandwidth frequency.? This is the type of opamp that the universal opamp models well.
However rail-to-rail opamps usually have transconductance type output stages so that their open loop output impedance is much higher, typically several k-ohms at high frequencies.? This is not always specified on the data sheet, but is critical for building a realistic model.? Perhaps that is what is missing from your simulation of the MCP6292. |
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