\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\usepackage{color}
\pagestyle{empty}
\begin{document}
\begin{equation*}
  u(t) = k_p e(t) + k_i \int_0^t e(\tau)\,d\tau + k_d \frac{de}{dt},
\end{equation*}
\end{document}