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Re: inverting opamp simulation: rapid component variation
John Woodgate
In message <CALBs-TimcdbfLAxu36m7Ee1HQ-dynXhchgbbKNqC+zGjJWvJWw@...>, dated Mon, 15 Apr 2013, Andy <Andrew.Ingraham@...> writes:
Indeed: in that case the gain formula gets more complicated, but the output is still a sine wave unless there is slew-rate limiting (aka 'transient harmonic distortion'). -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: All_Files.Htm
Same problem with Safari browser on Mac.
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Jim Wagner Oregon Research Electronics ----- Original Message -----
From: "Andy" <Andrew.Ingraham@...> To: LTspice@... Sent: Monday, April 15, 2013 7:29:17 AM Subject: Re: [LTspice] Re: All_Files.Htm Like the question about labeling hundreds of nodes, that doesn'tIt is a pain in the neck having to download it every time (or to fine [OOPS- find]Can you save it to your desktop, to make it easier to find? always work. I already have way too much stuff on my Desktop. Also, one of the computers is shared and I like to keep my regular files separate from my wife's if possible so we don't clutter each other's workspaces. That and my experience suggest that it's not a Yahoo thing but somethingI personally doubt it's a Microsoft 'improvement'. The computer I first noticed this on, was not doing automatic Microsoft updates, and I was not and am not using a Microsoft web browser. It's been noticed on a variety of web browsers. I think it is odd that they should all start misbehaving at the same time. I wondered if maybe Yahoo did this as a security enhancement in Yahoogroups: disabling the ability to directly load and run user-uploaded HTML files. It could even be that Microsoft made an "improvement" in IE to counteract Yahoo's security enhancement. :-) Also, given the way Yahoo serves things to users worldwide, sometimes there are differences between what you get and what I get, because we access different Yahoo servers even to access the same file. They don't seem to keep all their servers in sync. Andy [Non-text portions of this message have been removed] |
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Re: inverting opamp simulation: rapid component variation
--- In LTspice@..., John Woodgate <jmw@...> wrote:
John, This is true only at low frequcncies, and that's the reason the OP wants to know the effect as a function of frequency. Obviously, he needs to do this in the time domain for each frequency of interest. This type of problem has been discussed in this group relative to switch mode power supplies. In effect, time domain methods are used to get a pseudo frequency domain response. Rick |
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Re: inverting opamp simulation: rapid component variation
Doesn't varying R2 just vary the gain by which the DC input voltage isWithin the range where the op-amp has infinite gain, sure. At 1 MHz, I doubt it. He's talking about R2 variations at high frequencies, getting Bode plots. Under those conditions, the assumption falls through. Think about what happens at the output node when the op-amp is totally unresponsive (no current from its output pin, take the op-amp out of the circuit). Andy |
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Re: inverting opamp simulation: rapid component variation
--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
What I mean here is, in the circuit whether it is 10KHz variation of R2 or that of vin, your opamp always 'thinks' the same- it is working at 10KHz.Now coming to the issue in thread, I have this feeling that frequency isI am not sure what you mean. But an op-amp is no different than other This motivates me to put this hypothesis that i can plot the Bode due toThat's an interesting hypothesis, but I think it's not true. I think Could you kindly show it by a simulation that hypothesis is wrong? One thing I also just noticed about your earlier circuit, was that youThanks for pointing it out. That was unintentional and my carelessness. Due to this comment( and after changing amplitude of sinusoid) I got it today what Sedra means when he writes that limited bandwidth is linear phenomenon and doesn't cause distortion (while SR does).
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Re: All_Files.Htm
John Woodgate
In message <CALBs-TjeU10HN8E+Ba97R=LTNiyy-2ar5jyNQunNBcHqRv1Hqw@...>, dated Mon, 15 Apr 2013, Andy <Andrew.Ingraham@...> writes:
Also, given the way Yahoo serves things to users worldwide, sometimes there are differences between what you get and what I get, because we access different Yahoo servers even to access the same file. They don't seem to keep all their servers in sync.That could explain why some of us now don't see the problem. But I'm not sure that using a non-Microsoft browser fully insulates one from Microsoft 'improvements'. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: inverting opamp simulation: rapid component variation
John Woodgate
In message <CALBs-TjHj0Lx41mORJzKDHfd+kPbe+U=GYY+WhLO1MsP+7LKGw@...>, dated Mon, 15 Apr 2013, Andy <Andrew.Ingraham@...> writes:
That's an interesting hypothesis, but I think it's not true. I think that varying R2 (while a DC signal is placed at the input to the op-amp) is very different than simply applying a varying signal to the amp's input. I suspect that if you try it (with .TRAN analysis) you would see different results.Doesn't varying R2 just vary the gain by which the DC input voltage is multiplied to produce the output? So if R2 varies sinusoidally at frequency f, the output will be a sine wave at frequency f. Vout = Vin*R2/R1 If R2 = R*sin(2*pi*f*t), Vout = (Vin/R1)*R*sin(2*pi*f*t) -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: inverting opamp simulation: rapid component variation
Now coming to the issue in thread, I have this feeling that frequency isI am not sure what you mean. But an op-amp is no different than other components. Frequency applies to every thing in the circuit, not just op-amps. This motivates me to put this hypothesis that i can plot the Bode due toThat's an interesting hypothesis, but I think it's not true. I think that varying R2 (while a DC signal is placed at the input to the op-amp) is very different than simply applying a varying signal to the amp's input. I suspect that if you try it (with .TRAN analysis) you would see different results. One thing I also just noticed about your earlier circuit, was that you were varying R2 between 3000 and -1000 ohms. Did you really intend for R2 to go negative? Regards, Andy |
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Re: All_Files.Htm
Like the question about labeling hundreds of nodes, that doesn'tIt is a pain in the neck having to download it every time (or to fine [OOPS- find]Can you save it to your desktop, to make it easier to find? always work. I already have way too much stuff on my Desktop. Also, one of the computers is shared and I like to keep my regular files separate from my wife's if possible so we don't clutter each other's workspaces. That and my experience suggest that it's not a Yahoo thing but somethingI personally doubt it's a Microsoft 'improvement'. The computer I first noticed this on, was not doing automatic Microsoft updates, and I was not and am not using a Microsoft web browser. It's been noticed on a variety of web browsers. I think it is odd that they should all start misbehaving at the same time. I wondered if maybe Yahoo did this as a security enhancement in Yahoogroups: disabling the ability to directly load and run user-uploaded HTML files. It could even be that Microsoft made an "improvement" in IE to counteract Yahoo's security enhancement. :-) Also, given the way Yahoo serves things to users worldwide, sometimes there are differences between what you get and what I get, because we access different Yahoo servers even to access the same file. They don't seem to keep all their servers in sync. Andy |
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Re: Step a resistor over time
Hi Andy,
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Thanks for your response, but I do understand step vs slope. My question was actually about some difference in the syntax of the statement examples (which I couldn't detect). For some reason I was thinking that some subtle difference was making the first example actually step. But after closer inspection, I see that they both change in slopes, but the chosen values just force the slopes to be short. Sometimes I miss the obvious... Thanks, Mike --- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
But I can't seem to see what differentiates the step version from the slope version.The difference is the shape of the curves. They are both PWL |
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Re: inverting opamp simulation: rapid component variation
Hello All,
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@ Andy& Jim:Thanks for your input on tmax in .tran analysis. It was really useful and I plan to have a different thread on this soon. Now coming to the issue in thread, I have this feeling that frequency is just a frequency for an opamp, Whether it is that of input source or that of any component variation. This motivates me to put this hypothesis that i can plot the Bode due to rapid variation of R2 by just assuming R2 to be constant at its maximum value and sweeping the frequency of input vi (Vi should be changed to AC source). Here is setup files to show this: In inv_opm_freq_respns.asc I have setup to plot frequency sweep. I select three frequncies: 10KHz, 200KHz, 750KHz. I noticed that at the first two frequencies output is constant and at around 750KHz it rolls down by 3dB. Now in setup inv_opm_tran.asc, I do a transient analysis. I stepped R2 with above three frequencies and found that as suspected, output have same amplitude at 10KHz and 200KHz,and lower at 750KHz. As always, I especially seek views of people like Helmut, Andy, Jim, John , analogspiceman,chris to see if there is any fallacy in my understanding. Conference date has been extended to I have ample time to go deep down the problem. Thanks. --- In LTspice@..., Jim Wagner <wagnejam99@...> wrote:
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Re: THD of a sine with a small dent at crossover
Hello John,
You are getting these results because of your very shortThis was indeed the trick to get a "useful" result for THD in the .FOUR report. I have had used 10us rise and fall time in my example which I uploaded yesterday. Best regards, Helmut --- In LTspice@..., John Woodgate <jmw@...> wrote:
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Re: THD of a sine with a small dent at crossover
John Woodgate
In message <kkfbb8+osfi@...>, dated Sun, 14 Apr 2013, Echidna <mchambin@...> writes:
Indeed, I was tricked by the .FOUR function default calculation on 9 harmonics only. I tried with 99 harmonics and got a much different result.You are getting these results because of your very short rise and fall times and short 'crossover' pulses. If you do an FFT from 'View' you can see that the harmonic spectrum goes to well over 30 MHz. This isn't realistic for an audio amplifier, if that is what you are working on. But calculating THD by 'adding' (r.s.s.-wise) the harmonic amplitudes is seriously error-prone in my experience. It's much better to notch out the fundamental with a filter (simulated notch filters always work well, unlike real ones) and measure the r.m.s. value of what is left. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: High-power Infrared LED model desired
John Woodgate
In message <kkf8qp+pa6i@...>, dated Sun, 14 Apr 2013, sawreyrw <sawreyrw@...> writes:
Get over it.It's well-known to be incurable. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: All_Files.Htm
John Woodgate
In message <CALBs-TgwdGnyE+6k-DsnYM_d3xZ2OrmE-xvRep2TEYTBQCGQuQ@...>, dated Sun, 14 Apr 2013, Andy <Andrew.Ingraham@...> writes:
It is a pain in the neck having to download it every time (or to fine the copy I downloaded last week), but it does work.Can you save it to your desktop, to make it easier to find? I didn't do anything. That and my experience suggest that it's not a Yahoo thing but something on individual computers, probably a Microsoft 'improvement'. I have found IE8 going unstable twice in the last few months, showing strange and unpredictable behaviour. I have had to use the Tools => Advanced => Reset option, but that wasn't to fix the 'all_files' problem. Some web sites think I am using an earlier version, perhaps IE6, and complain about it, but I am definitely not. -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK |
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Re: Germanium transistor
Hi Jim.
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Thanks for your comment on the type of material the transistor. I removed a tag MFG=Germanium-type. Use the my Standard.zip file. Bordodynov. 12.04.2013, 20:10, "gr8wi9" <boothjg@...>: --- In LTspice@..., ¨¢???????? ?????????¡Á <BordodunovAlex@...> wrote:I don't see either of these in the standard library. I placed a pnp in a new schematic then right-click Pick New Transistor. I just did a sync release too. Decades ago 2N2955 was a silicon part (complementary to 2N3055). |
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Re: Tutorial version of Joule-Thief
On Sat, 13 Apr 2013 15:47:49 -0000, Tim wrote:
I just uploaded a another copy of the JT, because I wnat toI just posted up an example I wrote some time back. I added a comment or two to it before posting, though. It's in the Temp directory and called Joule_Thief_jk1.asc. It uses the basic energy equation to develop the expected peak current required. It's ability to calculate the exact frequency and the exact peak current given a specific transistor is only approximate, though. The base resistance calculation is only very approximate. Some tweaks are included to allow closer approximations. Note, the inductor coupling constant is given as 1 -- in reality it never will be. Feel free to adjust the equations to take a more realistic value into account. Also, I have an additional paper I wrote on the Joule Thief that includes details the above considerations plus others, such as Bmax, in those cases where an air core isn't used. The Bmax value places additional constraints on the choice of inductance value vs frequency, to avoid saturation effects due to volt-seconds (which the Joule thief doesn't not require and works perfectly well avoiding.) If interested in the paper, feel free to write and I will send it along in an email (PDF form.) Jon |
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Re: inverting opamp simulation: rapid component variation
Jim Wagner <wagnejam99@...> wrote:
You would expect one peak to be quite a different from the other, because it isIndeed they were; VERY different. But that was not what stood out. I expected all of the positive peaks (at a given frequency, and perhaps after the first couple of cycles) to look about the same as each other and to reach the same value as one another. Instead, what I saw was that the positive peaks never "leveled off" to the same value. Some were only 0.38V while others reached 0.55V. Zooming in showed that some peaks were very narrow and others were broader, and had a distinctly "sampled" appearance. Turning on "Mark Data Points" (right-click on the waveform plot window) showed that it had something to do with how closely spaced the data points were: not enough to reveal the true detail of the peaks. The negative peaks, by contrast, were smooth and round. But I wasn't looking at those. If this doesn't make sense, run the simulation and see what I mean. I doubt there is much loop gain at all at 1 MHz. Andy |
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Re: Step a resistor over time
But I can't seem to see what differentiates the step version from the slope version.The difference is the shape of the curves. They are both PWL (piecewise linear). The step one changes in steps, abruptly, followed by periods where the resistance stays fixed. The slope one changes like a triangular wave. Plot out the values to see for yourself. Andy |
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Re: I need 74ls193 for LTSpice
The similation file of 74HC193 is bellow site.... As you probably know already, the 74HC193 and 74LS193 are completely different technologies. The two chips might be interchangeable, and the 74HC part might be easier to obtain today, but note that the SPICE model for one would not be a good choice to use for the other part. Just beware. Andy |
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