LPV321 Datasheet, PDF (12/21 Pages) National Semiconductor (TI) – General Purpose, Low Voltage, Low Power, Rail-to-Rail Output Operational Amplifiers

Application Notes (Continued)
DS100920-14
FIGURE 9. Simple Low-Pass Active Filter
DS100920-15
FIGURE 10. Frequency Response of Simple Low-pass
Active Filter in Figure 9
Note that the single-op-amp active filters are used in to the
applications that require low quality factor, Q (≤ 10), low fre-
quency (≤ 5KHz), and low gain (≤ 10), or a small value for the
product of gain times Q (≤ 100). The op amp should have an
open loop voltage gain at the highest frequency of interest at
least 50 times larger than the gain of the filter at this fre-
quency. In addition, the selected op amp should have a slew
rate that meets the following requirement:
SlewRate ≥ 0.5 x (ω_HV _OPP) X 10^−6V/µsec
Where ω_H is the highest frequency of interest, and V_OPP is
the output peak-to-peak voltage.
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