It is my understanding that you are trying to plot a sine wave with a frequency up to 1MHz.
According to the Nyquist–Shannon sampling theorem, the sample rate must be at least twice the bandwidth of the signal to avoid aliasing, a type of distortion that occurs when the sample rate is too low.
Here, in the following implementation, I have increased the sampling rate for better resolution.
sig_amp = 2.8; %amplitude
fs = 1*1000*1000; %signal frequency Hz
sampleRate = 4*1000*1000;
numSamplesPerCycle = floor(sampleRate/(fs));
T = 1/(fs); %sampling period
timestep = T/numSamplesPerCycle;
t = (0 : timestep : 5-timestep)';
x = sig_amp*sin(2*pi*fs*t)';
plot(t,x,'.-');
xlabel('temps (s)');
ylabel('Tension de sortie (V)');
title('Signal versus Time');
grid on
