LM148/LM248/LM348
Typical Applications—LM148
(Continued)
A 4th Order 1 kHz Elliptic Filter (4 Poles, 4 Zeros)
00778614
R1C1 = R2C2 = t
R'1C'1 = R'2C'2 = t'
f
C
= 1 kHz, f
S
= 2 kHz, f
p
= 0.543, f
Z
= 2.14, Q = 0.841, f'
P
= 0.987, f'
Z
= 4.92, Q' = 4.403, normalized to ripple BW
Use the BP outputs to tune Q, Q', tune the 2 sections separately
R1 = R2 = 92.6k, R3 = R4 = R5 = 100k, R6 = 10k, R0 = 107.8k, R
L
= 100k, R
H
= 155.1k,
R'1 = R'2 = 50.9k, R'4 = R'5 = 100k, R'6 = 10k, R'0 = 5.78k, R'
L
= 100k, R'
H
= 248.12k, R'f = 100k. All capacitors are 0.001 µF.
Lowpass Response
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