LMF100_15 Datasheet, PDF (19/40 Pages) Texas Instruments – LMF100 Dual High-Performance Switched Capacitor Filters

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Device Functional Modes (continued)
LMF100
SNOSBG9B – JULY 1999 – REVISED JUNE 2015
Figure 42. MODE 1b
Figure 43. MODE 2
8.4.1.5 MODE 3: Highpass, Bandpass, Lowpass Outputs (See Figure 44)
f₀
=
f_CLK
100
´
R2 _{+ 1 or} f_{CLK ´}
R4
50
R2
R4
(35)
Q = quality factor of the complex pole pair =
R2 R3
R4 ^´ R2
(36)
H_OLP
=
Highpass
gain
at
æ
ç^f
è
®
f_CLK
2
ö
÷
ø
=
- ^R2
R1
(37)
H_OBP
=
Bandpass
gain
as (f
®
f₀ ) =
- ^R3
R1
(38)
H_OLP
=
Lowpass
gain
(as
f
®
0)
=
R4
-
R1
(39)
Circuit
dynamics :
R2
R4
=
H_OHP
H_OLP
; H_OBP
=
H_OHP ´ H_OLP ´ Q
(40)
H_OLP(peak) @ Q ´ H_OLP (for high Q ' s)
(41)
H_OHP(peak) @ Q ´ H_OHP (for high Q ' s)
(42)
8.4.1.6 MODE 3a: HP, BP, LP and Notch With External Op Amp (See Figure 45)
f₀
=
f_CLK
100
´
R2 _or f_{CLK ´}
R4 50
R2
R4
(43)
R2 R3
Q = _R4 ´ _R2
(44)
R2
H_OHP = - _R1
(45)
R3
H_OBP = - _R1
(46)
R4
H_OLP = - _R1
(47)
f_n
=
notch
frequency
=
f_CLK
100
R_{h or} f_CLK
R_l 50
R_h
R_l
(48)
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