MCP6L1 Datasheet, PDF (13/32 Pages) Microchip Technology – 2.8 MHz, 200 μA Op Amps

4.7 Application Circuits
4.7.1 ACTIVE LOW-PASS FILTER
Figure 4-6 shows a second-order Butterworth filter,
with a 10 Hz cutoff frequency and a gain of +1 V/V,
using a Sallen Key topology. Microchip’s FilterLab^®
software designed the filter, then the capacitors were
reduced in value (using the same program).
R₁
18.2 kΩ
V_IN
R₂
29.4 kΩ
C₂
470 nF
C₁
1.0 µF
MCP6L1
V_OUT
FIGURE 4-6:
Sallen Key Topology.
Figure 4-7 shows a filter with the same requirements,
except the gain is -1 V/V, in a Multiple Feedback topol-
ogy. It was designed in a similar fashion using Filter-
Lab^®.
R₁
54.9 kΩ
V_IN
C₂
820 nF
R₂
25.5 kΩ
R₃
25.5 kΩ
C₁
220 nF
MCP6L1
V_DD/2
V_OUT
FIGURE 4-7:
Multiple Feedback Topology.
MCP6L1/1R/2/4
© 2009 Microchip Technology Inc.
DS22135A-page 13