\documentclass[transparent, x11names]{standalone}
\usepackage{tikz, ubuntu}
\usepackage[utf8]{inputenc}

\usepgflibrary{arrows.meta} % Biblioteca de flechas
\tikzset{help lines/.style={gray,very thin}}

\begin{document}
\begin{tikzpicture}
	\draw [red, dotted,step=0.5] (0,0) grid (5,5);
	\draw [semithick, blue,-Stealth] (0,2.5)--(5.1,2.5) node [right]{$t$};
	\draw [semithick, blue,-Stealth] (0,4)--(5.1,4) node [right]{$t$};
	\draw [semithick, blue,-Stealth] (0,0)--(0,5);
	\node at(6,4.5){$v_m(t)$};
	% Señal moduladora
	\draw [semithick, Green2] (0,4.5)--(1,4.5)--(1,3.5)--(2,3.5)--(2,4.5)--(3.5,4.5)--(3.5,3.5)--(4,3.5)--(4,4.5)--(4.5,4.5)--(4.5,3.5)--(5,3.5);
	% Portadora
	\draw [domain = 0:5, samples=300, smooth, color=Maroon1] plot(\x,{2.5+0.5*sin(3000*\x))});
	\node at(6,3){$A\,cos(2\pi f_ct)$};
	% Salida de OOK
	\draw [domain = 0:1, samples=300, smooth, color=Red1] plot(\x,{1+0.5*(sin(3000*\x)})--(1,1)--(2,1);
	\draw [domain = 2:3.45, samples=300, smooth,color=Red1] plot(\x,{1+0.5*(sin(3000*\x)})--(3.5,1)--(4,1);
	\draw [domain = 4:4.5, samples=300, smooth,color=Red1,-Stealth] plot(\x,{1+0.5*(sin(3000*\x)})--(4.5,1)--(5.1,1) node [right]{$t$};
	\node[] at(6,1.5){$v_{AM}(t)$};
	\node[font=\small, align=center] at (3,5.5){Señales de Modulación \\Digital de Amplitud (OOK)};
\end{tikzpicture}
\end{document}