my simulation for a linear to logarithmic converter gives some confusing results - output Vout2 gives somewhere not a million miles away from what it should be although it’s not that correct either, but at least when you zoom in on the trace you can see the shape is something like what you would expect.
the bit i find really confusing, is the output Vout. This is obviously completely incorrect (in the sense its not what happens in real life), the output Vout should be centred around 0. Why the offset?
Unless you have this box checked in the simulator settings, M is interpreted as milli by SPICE because it’s case-insensitive. The typical way is to write meg to specify megaohm. I don’t know if that’s the cause of your issue, but it’s worth mentioning.
If you still have problems, I suggest either uploading your project in a ZIPped folder or giving us a copy/paste of the SPICE netlist text. The screenshot can’t tell us how you set up each component and if you did it correctly.
thank i didn’t know that, it does make a difference but the problem is still there - output from Vout is all wrong, despite that the output from vout2 is quite feasibly correct now
One thing I was able to notice from your netlist is that you haven’t set the “Alternate Node Sequence” for the PNP transistors. The default node order for BJTs is C B E. Since the symbols you used are E B C, you need to put 3 2 1 in for the “Alternate Node Sequence” as shown below:
I still don’t have enough info to run your project, since your SPICE libraries aren’t in your project folder and are somewhere in your Documents folder instead: C:\Users\phili\Documents\_spice models\
That’s normally fine to do, but keep in mind that it screws up portability if you need to send your project to someone else and have them see exactly what you see.
