Italic or upgright font for circuit components
These rules, ISO 31-13:1992 apply to scientific papers, journals, datasheets and books. 

"Schematic or Logic or circuit " diagrams detailed rules , and other document types used in electrotechnology, are provided in the international standard IEC 61082-1:2015 and do not use the same rules.

Learning to adopt standards makes documents look more professional and readable by others, but there are many styles and many existing standards for different document content types.