Re: The not-all-that-low distortion sine wave oscillator in a faster simulating version

On 20/12/2024 1:53 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vk0ehh$2o9dc$1@dont-email.me...

On 19/12/2024 2:10 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vk00um$2i900$1@dont-email.me...

On 19/12/2024 6:00 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vjtgnp$24ubg$1@dont-email.me...

I've been playing with the circuit, and have got rid of one op amp, which made the simulation run much faster, but didn't help
the
distortion performance.
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Swapping the LT1115 for the LME49710 speeded up the simulation a bit more, but didn't make any difference to the distortion
either. A few of the ferrite beads have gone too.
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I got a simulation speed of about 30us/s so I didn't wait the nearly 4 days it would take to complete.
I did an FFT on the first few cycles and it does look 100dB down up to 1.5MHz.

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It ran at 68msec/sec for me and takes a couple of minutes to run the full ten seconds.

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I used the circuit from your third post. One op amp had to be moved down a bit into position and then I hit simulate.
To be sure we're talking about the same circuit I've reposted it below.
I'm using LTSpice 24.0.12 with no new model updates available as of this post.

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And I'm using LTSpice XVII(x64)(17.0.37.0) up-dated recently.
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I finally got your version to work. As you say, U1 had to be moved into place, but I also had to change C10 on the output of U4.
I'd specified the capacitance as 3.3u. but the "u" symbol had vanished. When I specified the capacitance as 3300n everything
worked fine.

 C10 is definitely 3.3u here. I tried changing it to 3300n but still less than 30us/s when I start the simulation.

We do seem to be using different versions of LTSpice. There are subtle ways the simulation can get screwed up and slowed down. John May emphasised that using trapezoidal integration rather the modified trapezoidal or Gear made a positive difference when you were worried about distortion.
<snip>

Also is there any way in LTSpice to find a component?

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Inspection works fine for me. Professional circuit diagrams tend to get re-numbered before they are released to production so
the numbers run from left to right across the sheet in bands, then from top to bottom as you moved down from the top band to the
bottom band.

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What would you do when a change is required which requires an additional component such as an additional resistor or capacitor?

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I wasn't responsible for keeping production drawings up to date, and the people who were had a bunch of conflicting priorities to
reconcile.

 Ok - that's one way to avoid the question.

I know what I'd do, but I don't have background information to give a particularly useful response. Everybody has their own opinions on what circuit diagrams ought to look like, and companies need to get their circuit diagrams into a form where the engineers and various sorts of technicians can read them easily, but there's a lot of variation between companies, and I know that US companies made different choices from the UK and Dutch companies that I worked for.
--
Bill Sloman, Sydney