LT1366/LT1367
LT1368/LT1369
U
TYPICAL APPLICATIONS
10k
the 2 op amp loop to create a negative summing junction
at A1’s positive input1. The circuit has low sensitivities for
center frequency and Q, which are set with the following
equations:
+
V
2
3
–
1
1/2 LT1366
V
OUT
V
IN
+
ω02 = 1/(R1 • C1 • R2 • C2)
SIGNAL AMP
where,
1M
R1 = 1/(ω0 • Q • C1) and R2 = Q/(ω0 • C2).
5
+
The DC bias applied to A2 and A4, half supply, is not
needed when split supplies are available. The circuit
swings rail-to-rail in the passband making it an excellent
anti-aliasingfilter forADCs. The amplitude response is flat
to 1kHz then rolls off at 80dB/decade.
7
CANCELLATION AMP
1/2 LT1366
6
–
22pF
1M
1366 F10
1James Hahn, “State Variable Filter Trims Predecessor’s Component Count,” Electronics, April
21, 1982.
Figure 10. Input Bias Current Cancellation
180
144
108
0
–20
–40
–60
–80
GAIN
PHASE
V
CC
72
36
0
R
P
–36
–72
–108
+
10k
1/2 LT1366
–
–144
–180
10k
R
L
100
1k
FREQUENCY (Hz)
1366 F09
1366 F11
Figure 9. Frequency Response of 4th Order Butterworth Filter
Figure 11. Rail-to-Rail Potentiometer Buffer
16
Linear [ Linear ]
