LMF100_15 Datasheet, PDF (17/40 Pages) Texas Instruments – LMF100 Dual High-Performance Switched Capacitor Filters

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Device Functional Modes (continued)
8.4.1.1 MODE 1: Notch 1, Bandpass, Lowpass Outputs:
f_notch = f₀ (See Figure 40)
f₀
=
center
frequency
of
the
complex
pole
pair
=
f_CLK
100
or
f_CLK
50
f_notch = center frequency of the imaginary zero pair = f₀
H_OLP
=
Lowpass
gain
(as
f
®
0)
=
R2
-
R1
H_OBP
=
Bandpass
gain
(at
f
®
0)
=
R3
-
R1
H_ON = Notch output gain as
f ®0
f ® f_CLK / 2
= ^-R2
R₁
Q
=
f₀
BW
=
R3
R2
= quality
factor
of
the complex pole pair
BW = the - 3 dB bandwidth of the bandpass output.
Circuit dynamics : H_OBP1 = Q
H_OLP
=
H_OBP
Q
or
H_OBP
= H_OLP
´Q
= H_ON ´ Q
H_OLP(peak) @ Q ´ H_OLP (for high Q ' s)
8.4.1.2 MODE 1a: Noninverting BP, LP (See Figure 41)
f₀
=
f_CLK
100
or
f_CLK
50
H_OLP = -1; H_OLP(peak) @ Q ´ H_OLP (for high Q ' s)
R3
H_OBP1 = - _R2
H_OBP2 = 1 (noninverting)
Circuit dynamics : H_OBP1 = Q
Note: VIN should be driven from a low-impedance (<1 kΩ) source.
LMF100
SNOSBG9B – JULY 1999 – REVISED JUNE 2015
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(11)
(12)
(13)
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Figure 40. MODE 1
Figure 41. MODE 1a
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