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I'm working with the HSPICE MOSFET Models Manual for a university project.

In some equations there's this \$Þ\$ symbol. For example from an equation regarding the Shichman-Hodges Model: $$ W_\text{eff}=M\cdot \left( W_\text{scaled} \cdot WMLT + XW_\text{scaled} - 2 Þ \text{WD}_\text{scaled} \right) $$ It appears in numerous equations. What does Þ mean there?

Sky V
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  • Not in the index / units / symbols? Usually are. – Solar Mike Feb 12 '21 at 21:14
  • Sadly no. The first occurence of the symbol in the entire PDF is inside an equation, as is the last. Spent a couple of minutes to go through every occurence with the search function, but every single occurence is inside an equation, except for a occurrence, where it's part of a math term in a table. – Sky V Feb 12 '21 at 21:21
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    `Þ` is `thorn` which is a letter from old english or norse alphabet .... i wonder if the letter should be a greek letter `ϕ` phi – jsotola Feb 12 '21 at 21:31
  • not a single greek letter phi exists in the entire document. The parameters are usually spelled out due to the spice language, and in fact, "PHI" exists numerous times. In fact, equations exist where PHI and Þ exist in the same equation. So I doubt that it's supposed to be a greek phi. – Sky V Feb 12 '21 at 21:40
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    It can be that the character is improperly decoded. In some help file, the \$\pi\$ is rendered as an emboldened **p**. If this is the case, just consider whatever character you want, as long as it's consistent (and not a duplicate)... – a concerned citizen Feb 12 '21 at 23:11

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I believe you are referencing this 2005 version of the document (PDF page 151). If you look at the same equation in this older 1998 version of a similar document (PDF page 6), this symbol is replaced by a multiplication dot, but without a space after it. Both are snipped and shown below for direct comparison:

enter image description here Therefore, I believe there's an encoding error in the PDF (as suggested in the comments), which is caused by the lack of a space after the dot. So simply treat that symbol as a multiplication, or use the older document (if you can).

Ste Kulov
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  • This seems to be the answer. With your hint, I've checked the BSIM lvl13 model in the 2005 document and on page 334, the first \$xeta=...\$ equation exists in pretty much the same form in the original paper by Sheu, Scharfetter et al. (BSIM: Berkeley Short-Channel IGFET Model for MOS Transistors). The thorn symbol is simply an implied multiplication in section C.2. Thank you very much for the hint! – Sky V Feb 13 '21 at 18:47