Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- LTspice
- Messages
Search
|
Re: List Addresses Hacked
rainbowsally
I hate when I do that... 500-1000 emails a "month", not a "day". Add one for this correction. :-(
toggle quoted message
Show quoted text
Heinz-W. Schockenbaum wrote:
|
|
Recommended alternate electronics group (was Re: Re: Kevin -- Tip: a cheap full load resistor)
Electronics_101 <> is quite a suitable place to discuss such matters. We also use LTspice (and whatever other tools are necessary or handy, up to and including oscilloscopes and soldering irons) to achieve the understanding.
toggle quoted message
Show quoted text
Donald. -- *Plain Text* email -- it's an accessibility issue () no proprietary attachments; no html mail /\ ascii ribbon campaign - <www.asciiribbon.org> ----- Original Message -----
From: "rainbowsally" <rainbowsally@...> |
|
Re: List Addresses Hacked
rainbowsally
That's right. We get 500-1000 emails a day -- April was even more than that.
toggle quoted message
Show quoted text
Heinz-W. Schockenbaum wrote:
|
|
Re: is there a model or subckt for the PWM chip SG3524?
rainbowsally
Hi Gandolf.
First pass, yer parts count has just gone way way WAY down. Check your folder for the "rs-01" mods. I left the holes where the old parts were and added jumpers to show where the new connections go... if this still works for you. Check your original file and verify that the wave forms in/out for the opamp are identical. There is nothing really loading that source so the opamp (buffer) is unnecessary as currently implemented. Note: There's an NE555.asc file in the examples folder. It shows that the CV is 5K to Vcc and 10K to Gnd. You don't need a resistor on the control voltage output. Just the cap. And if you were attempting to pull it down, use a much smaller resistor to do that, but chances are you want to stay with the default. :-) |
|
Re: is there a model or subckt for the PWM chip SG3524?
rainbowsally
Hi, Gandolf
First as to your questions... Gandolf wrote: Thanks, rainbowsally, much appreciated.Yes. It's an op amp w/ jfet inputs (4 uA input currents measured at the op amp). Probably even a 741 would work though. Is it OK that the TI model has the filename extension .301 instead of .mod or something like that? (And why the heck did TI give it the .301 extension in the first place?)Notaclue. ;-) Might be a model revision number? Why do I have to keep increasing the time step to as high as 1ms (where it is right now) to get the sim to run without a "time step error" message?Good question. It may be that you had checked the 'skip initial operating point solution". This forced the circuit into a very non-linear range and the attempt to converge to realistic values for all the components (by iterations using Newton's method). General solution. Allow it to find the initial operating point, even if it runs a little slower. Why is it that the comparator is running in the sim even though I didn't include an .include command for its file in the folder?The comparitor didn't even show up on my schematic. I plugged in a LT1017 which looks like it's at least pin compatible for now. So many questions, so few years left....Mylar (film) generally has good temperature stability too. Good choice. PPS: the 555 will actually be the TLC555 from TI, CMOS version, that doesn't spike the supply rail nearly as badly as all the BJT versions, but I didn't bother trying to import a model and .asy for the CMOS 555.We might want to model it. Now for some feedback on your circuit. First of all, very nice schematic! Now for things that you might not have seen and/or that might be improved. These are general observations and may not be applicable to this exact circuit as I have not run it through anything but a cursory check so far. 1. Availability of parts models. As mentioned above, I don't think your comparator is an a standard LTSpice d/load. I used any old pin-comptible one that I found. This doesn't apply to the circuit itself, only to the simulation. 2. Dynamic range. I don't think you want the 10% hysteresis on the comparator (U4). That's the 100K from the output back to the non-inverting input. This will limit your ability to get vary narrow or vary large pulse widths and is unnecessary because you don't have noise on the inputs that could possibly cause a false trigger (seen as spike in the output). If you do get spikes in the output, you might want to decouple the supply to the comparator itself with something like ten ohm resistors and .1 caps. 3. R9 is unnecessary because the input impedance of the comparators is quite high and the output inpedance of the opamp is quite low. If for some reason the opamp isn't able to drive the tiny capacitance of the comparator input, then no problem but for this unity setup gain that's incredibly unlikely. 4. Your feedback network for the opamp is probably unnecessary. The 1K from out to the inverted input could probably be replaced by a short and the 100K (R8) could probably be eliminated. Basically what you have here is an offset adjustment that is almost certainly unnecessary. 5. Similarly, the 10K (R6) is probably unnecessary. The input current at the opamp is in the range of 37 pico amps (thousandths of milliamps). In applications where dc offsets are critical at each stage you may need to balance the voltage drops between the two inputs, but almost certainly not here. This stuff does affect cost and until I can think of something to write about switching power supplies which is presumably the actual topic at "Switcher CAD LTSpice" forum, hopefully no one will be too offended by these notes. If drilling holes isn't a cost issue, you might want to design them in and just put jumpers in some and leave the others empty so you can optionally use the resistors if you replace the opamps or comparators on your board with cheaper but adequate parts as prices and availability may fluctuate over time. Now I'll play with your model for a while (make the pots, etc.) and see what you've got going on. :-) Stay tuned. We may have a sub-forum coming for discussion of issues anyone thinks are off topic for this forum. |
|
Re: Kevin -- Tip: a cheap full load resistor
rainbowsally
It will be unmoderated. Will you be available to be a second owner in case something happens to me so it can be shut down if it gets out of control (trolls, spam, etc.)?
toggle quoted message
Show quoted text
Helmut wrote: Hello Kevin, |
|
Re: dual npn transistors and some obsolete op-amps
I see.. Thank you though..
toggle quoted message
Show quoted text
--- In LTspice@..., "Larry Beaty" <lbeaty@...> wrote:
|
|
Re: dual npn transistors and some obsolete op-amps
I also tried searching for it, and you were right, it was the first one on the search list.. sorry about that.. but uhhm, how do you convert that information to a spice model?
toggle quoted message
Show quoted text
--- In LTspice@..., John Woodgate <jmw@...> wrote:
|
|
Re: application upgrade
Mike has said, in the LTspice World Tour seminars, that the extended versions of LTspice are used internally within Linear for chip design. He has said, specifically, that certain features, that would make it "too easy" for other parties to replicate LT parts will never appear in the public version of LTspice.
Likewise, by inference, if someone asks for a change that would require changes by LT employees, I'd bet that the benefit would have to be very high. Jim Wagner Oregon Research Electronics On Aug 26, 2012, at 5:26 AM, Heinz-W. Schockenbaum wrote:
[Non-text portions of this message have been removed] |
|
Re: dual npn transistors and some obsolete op-amps
No, sorry, I have the device.
Larry From: LTspice@... [mailto:LTspice@...] On Behalf Of Shadow Sent: Sunday, August 26, 2012 11:41 AM To: LTspice@... Subject: [LTspice] Re: dual npn transistors and some obsolete op-amps What do you mean? Do you have the LTSPICE model of 2n2920?? If so, could you post here. It would be very helpful. --- In LTspice@... <mailto:LTspice%40yahoogroups.com> , "Larry Beaty" <lbeaty@...> wrote: [mailto:LTspice@... <mailto:LTspice%40yahoogroups.com> ] On Behalf Of Shadownetlist would be great.. |
|
Re: dual npn transistors and some obsolete op-amps
What do you mean? Do you have the LTSPICE model of 2n2920?? If so, could you post here. It would be very helpful.
toggle quoted message
Show quoted text
--- In LTspice@..., "Larry Beaty" <lbeaty@...> wrote:
|
|
Re: dual npn transistors and some obsolete op-amps
John Woodgate
In message <k1ddm4+i2u8@...>, dated Sun, 26 Aug 2012, Shadow <shadowvpr123@...> writes:
I need to simulate a circuit involving a dual npn transistor, specifically 2N2920 transistor,.. Well I can't find a model here... Could you help me out... Maybe i didn't search enough... Do you guys know where i can find that transistor? or any transistor model similar to 2N2920? Thanks..Maybe you didn't search enough. The first hit I get from Google leads to: Scroll down. The model looks very basic to me, but may be enough. If you want to investigate mismatches between the two devices, you will have to use some of LTspice's magic tricks. -- 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 |
|
Re: dual npn transistors and some obsolete op-amps
My inventory shows a 2N2925, but shows no listing for quantity. If you
want, let me know. Then I will search for it. Larry From: LTspice@... [mailto:LTspice@...] On Behalf Of Shadow Sent: Sunday, August 26, 2012 11:00 AM To: LTspice@... Subject: [LTspice] dual npn transistors and some obsolete op-amps Hello! Good day to all... I need to simulate a circuit involving a dual npn transistor, specifically 2N2920 transistor,.. Well I can't find a model here... Could you help me out... Maybe i didn't search enough... Do you guys know where i can find that transistor? or any transistor model similar to 2N2920? Thanks.. Also, about those obsolete op-amps, specifically LM101A and LM108, well I need those as well,.. There is a netlist that can be downloaded in Linear Technology, but uhhm, I don't know how to load a component using the netlists... A quick tutorial on how to create/load a model using the netlist would be great.. Sorry for the disturbance... Any suggestions would be helpful... |
|
Re: is there a model or subckt for the PWM chip SG3524?
rainbowsally
Cool. I'll go take a look.
Got one uploaded and another one brewing myself. Gandolf wrote: Thanks, rainbowsally, much appreciated.:-) Yuh never know, Gandolf. Time may be non-linear. It sure is on my 555 circuit. Thanks, by the way! |
|
Re: is there a model or subckt for the PWM chip SG3524?
rainbowsally
Hi Gandolf.
Gandolf wrote: Thanks, Rainbowsally, much appreciated.Here's my first hack at a 'solution'. 555-pw-mod-rs-01-100Hz-5KHz.zip The ramp using an adjustable current source (actual xistor in the circuit) looks good but seems to be off about 5-10 percent for what should have been 50% duty cycle so the collector of the current source is a little bit too sensitive to changes in voltage or there's a current leakage somewhere that I can't see. Of interest to others might be 1. An example of a 555 circuit (though we don't use the output). 2. the creation of a couple of pots, one for current and the other for voltage, both only require changing one parameter and in the case of the one used for changing current the parameter is 0-1 for 0 ohms to 1 meg -- the resistor could have been any value and it would still change proportionally -- and actually, I think that was a log taper formula or something on that one. |
|
dual npn transistors and some obsolete op-amps
Hello! Good day to all...
I need to simulate a circuit involving a dual npn transistor, specifically 2N2920 transistor,.. Well I can't find a model here... Could you help me out... Maybe i didn't search enough... Do you guys know where i can find that transistor? or any transistor model similar to 2N2920? Thanks.. Also, about those obsolete op-amps, specifically LM101A and LM108, well I need those as well,.. There is a netlist that can be downloaded in Linear Technology, but uhhm, I don't know how to load a component using the netlists... A quick tutorial on how to create/load a model using the netlist would be great.. Sorry for the disturbance... Any suggestions would be helpful... |
to navigate to use esc to dismiss