Why my low pass digital filter amplifies in the passband?
I found the mistake in my code:

when the Matlab's Filter Design &amp; Analisys Tool generates the cofficients, there are even the Gains for the every biquad section. Before the value goes out from one section, it must be multiplied with this gain.

So the right code is the following:

input = AmplitudeF8.';

delayline_lp = [0,0,0,0,0,0,0,0,0,0];
scale_values = [0.033199864272165251, 0.030083971778956442, 0.027859766117136031, 0.026439548658171989, 0.025749453352093145];
coeff_lp = [-1.7582972612745587, 0.89109671836321969, 2, 1, -1.5932765493727838, 0.71361243648860972, 2, 1, -1.4754804435926461, 0.58691950806119031, 2, 1, -1.4002643388507841, 0.50602253348347193, 2, 1, -1.3637162169443289, 0.46671403035270148, 2, 1];

for k=1:length(input)    
    y = input(k);

    for j=1:5 %the biquad sections
        w = y;
        for i=1:2
            w = w - (coeff_lp(((j - 1) * 4) + i) * delayline_lp(((j - 1) * 2) + i));
        end

        y = w;
        for i=1:2
            y = y + (coeff_lp(((j - 1) * 4) + i + 2) * delayline_lp(((j - 1) * 2) + i));
        end

        y = y * scale_values(j);

        delayline_lp(j * 2) = delayline_lp((j * 2) - 1);        
        delayline_lp((j * 2) - 1) = w;
    end

    output2(k) = y;
end


Then the C-Code for my MCU is (maybe is usefull for someone):

double Filter_IIR_Biquad_Sec( double signal, double *coeffs, double *scaleValues, double *delayLine, uint32_t nSections )
{
    uint32_t i, j;
    double y = signal;
    double w = 0.0;

    for ( j = 0; j &lt; nSections; j++ )
    {
        // The denominator
        w = y;
        for ( i = 0; i &lt; 2; i++ )
            w -= coeffs[ ( j &lt;&lt; 2 ) + i ] * delayLine[ ( j &lt;&lt; 1 ) + i ];

        // The numerator
        y = w;
        for ( i = 0; i &lt; 2; i++ )
            y += coeffs[ ( j &lt;&lt; 2 ) + i + 2 ] * delayLine[ ( j &lt;&lt; 1 ) + i ];

        y *= scaleValues[ j ];

        // Shift the register values
        delayLine[ ( j &lt;&lt; 1 ) + 1 ] = delayLine[ j &lt;&lt; 1 ];
        delayLine[ j &lt;&lt; 1 ] = w;
    }

    return y;
}


and now it works very well.