\begin{tikzpicture}
    % Configurações compartilhadas
    \pgfplotsset{
        my_axis_style/.style={
            width=5.5cm, height=4.5cm,
            axis lines=middle,
            xmin=0, xmax=8.5,
            ymin=-0.8, ymax=1.2,
            % Remove números e marcas dos eixos
            xtick=\empty, 
            ytick={-0.75,-0.5,-0.25,0.25,0.5,0.75,1.0},
            yticklabels=\empty, 
            extra y ticks={0},
            extra y tick labels=\empty,
            domain=0:8,
            samples=100,
            thick,
            % Rótulo do eixo Y à esquerda
            every axis y label/.style={at={(ticklabel* cs:0.95)}, anchor=east, xshift=-2pt},
            every axis x label/.style={at={(ticklabel* cs:0.95)}, anchor=north}
        }
    }

    % 1. Sinal Contínuo y(t)
    \begin{axis}[
        my_axis_style,
        title={\textbf{Contínuo: $y(t)$}},
        name=cont,
        ylabel={$y(t)$},
        xlabel={$t$},
        ytick=\empty % Sem grid no contínuo
    ]
        \addplot[blue, smooth] {exp(-0.3*x)*sin(deg(2*x))};
    \end{axis}

    % 2. Sinal Amostrado y(nTs)
    \begin{axis}[
        my_axis_style,
        title={\textbf{Amostrado: $y(nT_s)$}},
        name=amost,
        at={(cont.right of south east)}, 
        xshift=1.5cm,                     
        anchor=south west,
        ylabel={$y(nT_s)$},
        xlabel={$nT_s$},
        % Correção do Grid
        ymajorgrids=true,
        grid style={dashed, gray!30}
    ]
        \addplot[gray, dashed, opacity=0.2] {exp(-0.3*x)*sin(deg(2*x))};
        \addplot[blue, ycomb, samples=16, mark=*, mark size=1.5pt] {exp(-0.3*x)*sin(deg(2*x))};
    \end{axis}

    % 3. Sinal Digital yq[k]
    \begin{axis}[
        my_axis_style,
        title={\textbf{Digital: $y[k]$}},
        name=dig,
        at={(amost.right of south east)},
        xshift=1.5cm,
        anchor=south west,
        ylabel={$y[k]$},
        xlabel={$k$},
        % Correção do Grid
        ymajorgrids=true,
        grid style={dashed, gray!30}
    ]
        \addplot[gray, dashed, opacity=0.2] {exp(-0.3*x)*sin(deg(2*x))};
        \addplot[red, const plot, samples=16, mark=square*, mark size=1.5pt] {round(exp(-0.3*x)*sin(deg(2*x))*4)/4};
    \end{axis}

\end{tikzpicture}