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Chapter 3 Analog Output Waveforms
Selecting Components for Lowpass Filtering
To determine the value of the components in the circuit, fix R (10 kΩ is reasonable) and isolate
C from Equation 3-1 as follows:
(3-2)
The cut-off frequency in Equation 3-2 is f
c
.
For best results, choose a resistor that has the following characteristics:
• Low wattage of approximately 0.125 W
• Precision of at least 5%
• Temperature stability
• Tolerance of 5%
• AXL package (suggested)
• Carbon or metal film (suggested)
Choose a capacitor that has the following suggested characteristics:
• AXL or RDL package
• Tolerance of 20%
• Maximum voltage of at least 25 V
Adding Components for Lowpass Smoothing Filters on
Analog Output Signals
Using the circuit shown in Figure 3-8, you can use a two-component circuit to build a simple RC
filter with analog output. To build a lowpass filter for analog output, put a resistor in position A
and a capacitor in position B, as shown in Figure 3-9.
The SCB-68A ships with a surface mount 0 Ω resistor in the A position. You must remove the
resistor to use the position. Refer to Table 3-1 for component positions for both analog output
channels.
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