SPICE-Simulation using LTspice IV

Example:
Let us use the RC-LPF of the last chapter (R =10k / C = 10nF). The input is fed by a symmetric square wave
voltage (minimum amplitude value = 0V , maximum amplitude value = 1V , frequency = 1kHz).
If we use a simulation time of 20ms with a maximum time step of 100ns we meet the above recommendations as
follows:
a) The simulation time of 20ms is an integer multiple of the signal’s period time (1ms).
b) A maximum time step of 100ns is corresponding to a minimum sample frequency of 1/100ns = 10MHz.
This gives a Shannon corner frequency of 0.5 x sample frequency = 5MHz.
c) The number of true samples is 20ms / 100ns = 200 000. So we enter
in the FFT menu.
„131 072 sampled data points in time“
Now draw the circuit, set the properties of the voltage source, choose simulation time and time step and write the
directive to switch off the data compression.
The time domain simulation result (= input and the output voltage) should be presented in two plot panes.
Also “thick lines” are used for the curves (= button with the hammer / menu “waveforms”).
Now right click on
the input voltage
and choose “View”
and “FFT”
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