\begin{tikzpicture}
     
        % Desenha o comparador:
        \node [draw, circle, 
                minimum size=0.6cm, 
                fill=blue!20] 
              (comp) at (0,0) {};
        \draw (comp.north east) -- (comp.south west)
              (comp.north west) -- (comp.south east);
        \node [left=-1pt] 
                at (comp.center){\tiny $+$};
        \node [below]     
                at (comp.center){\tiny $-$};
        
        % Bloco do controlador:
        \node [draw,
            fill=blue!20,
            minimum width=2cm,
            minimum height=1.2cm,
            right=1cm of comp
        ]  (controlador) {$C(s)$};
        
        % Bloco da planta:
        \node [draw,
            fill=blue!20, 
            minimum width=2cm, 
            minimum height=1.2cm,
            right=1.5cm of controlador
        ] (sistema) {$G(s)$};
     
        % Bloco do sensor:
        \node [draw,
            fill=blue!20, 
            minimum width=2cm, 
            minimum height=1.2cm, 
            below right= 1cm and -0.25cm of controlador
        ]  (sensor) {$M(s)$};
        
        % Ramos de sinais:
        % - Erro:
        \draw[-stealth] (comp.east) -- (controlador.west) 
        node[midway,above]{$e$};
    
        % - Controle:
        \draw[-stealth] (controlador.east) -- (sistema.west) 
        node[midway,above] (u) {$u$};
        
        % - Saída:
        \draw[-stealth] (sistema.east) -- ++ (1.25,0) 
        node[midway](saida){}
        node[midway,above]{$y$};
        
        % - Realimentação:
        \draw[-stealth] (saida.center) |- (sensor.east);
        \draw[-stealth] (sensor.west) -| (comp.south) 
        node[near end,left]{$y_m$};
        
        % - Referência:
        \draw[-stealth] (-1.25,0) -- (comp.west) 
        node[midway,above]{$y_{r}$};

    \end{tikzpicture}