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6.4 THD+N vs Frequency
20 20k50 100 200 500 1k 2k 5k 10k
f-Frequency-Hz
0.001
10
0.002
0.005
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
THD+N-TotalHarmonicDistortionPlusNoise-%
2Vrms600 W
2Vrms100kW
20 20k50 100 200 500 1k 2k 5k 10k
f-Frequency-Hz
0.001
10
0.002
0.005
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
THD+N-TotalHarmonicDistortionPlusNoise-%
X7R1 F,16V,0805m
X7R1 F,50V,1206m
1 Ffilmm
DRV601EVM Performance
Figure 12. THD+N vs Frequency (600- Ω Load)
The DRV601EVM uses a 1- µ F film capacitor for ac-coupling of the input signal. If a lower cost ceramic
capacitor, like a X7R is used, higher THD at low frequencies should be expected. Y5V capacitors show
even higher THD and cannot be recommended at all.
Figure 13. THD+N vs Frequency (600- Ω Load) Using X7R Input Capacitors
The X7R capacitors raise the 20-Hz THD from 0.003% to 0.04% or 0.07–20 times higher. If the cost
requirements for the system demand that an inexpensive capacitor is used, then select the X7R capacitor
with the highest voltage rating, as seen from the figure a 50-V X7R 1206 capacitor has 2x lower THD than
a 16-V X7R 0805 capacitor.
DRV601EVM 12 SLOU215 – January 2008
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