(c) The THD is obtained from the Fourier series for I(R) in the output file as 16.7 percent,
agreeing with the Fourier analysis in Examples 8-2 and 8-3. Note that the THD for
the square wave in the output file is 45 percent, which is lower than the 48.3 percent
computed in Example 8-3. The THD in PSpice is based on the truncated Fourier
series through n=15. The magnitudes of higher-order harmonics are not
insignificant for the square wave, and omitting them underestimates the THD. The
higher-order current harmonics are small, so there is little error in omitting them from
the analysis. The number of harmonics in the output file can be increased if desired.