2 0 Modes of Operation
The MF10 is a switched capacitor (sampled data) filter To
fully describe its transfer functions a time domain approach
is appropriate Since this is cumbersome and since the
MF10 closely approximates continuous filters the following
discussion is based on the well know frequency domain
Each MF10 can produce a full 2nd order function See Ta-
ble I for a summary of the characteristics of the various
modes
MODE 1 Notch 1 Bandpass Lowpass Outputs
f
notch
e
f
O
(See
Figure 7
)
e
center frequency of the complex pole pair
f
O
f
f
e
CLK
or
CLK
100
50
e
center frequency of the imaginary zero pair
e
f
O
f
notch
R2
H
OLP
e
Lowpass gain (as f
x
0)
e b
R1
R3
H
OBP
e
Bandpass gain (at f
e
f
O
)
e b
R1
b
R
2
f
x
0
e
H
ON
e
Notch output gain as f
x
f
CLK
2
R
1
Q
f
O
R3
e
BW
R2
e
quality factor of the complex pole pair
e
e
the
b
3 dB bandwidth of the bandpass output
BW
Circuit dynamics
H
OLP
e
H
OBP
or H
OBP
e
H
OLP
c
Q
Q
e
H
ON
c
Q
H
OLP(peak)
j
Q
c
H
OLP
(for high Q’s)
MODE 1a Non-Inverting BP LP (See
Figure 8
)
f
f
e
CLK
or
CLK
f
O
100
50
R3
e
Q
R2
H
OLP
e b
1 H
OLP(peak)
j
Q
c
H
OLP
(for high Q’s)
R3
R2
e
H
OBP2
1 (Non-Inverting)
Circuit Dynamics H
OBP1
e
Q
e
H
OBP1
b
Note
V
IN
should be driven from a low impedance (
k
1 kX) source
(
TL H 10399 – 16
FIGURE 7 MODE 1
TL H 10399 – 17
FIGURE 8 MODE 1a
9
NSC [ NATIONAL SEMICONDUCTOR ]
