Inline equation in latex with text

Enclose your formula in single $, as follows:

Text text text $ \some \math \commands $ more text text text.

Note that if you use double $$ instead, the formula will appear in it's own line, and the text will continue below.

It depends also on how you want your "variables" to appear; if you want them in the normal text font, then

$\textrm{Amplitude} = 0.3 \cdot \textrm{Max\_Amp\_Of\_Signal}$

is sufficient. Notice the \_ to get the underscore, because _ has a special meaning in LaTeX.