LMV321M5X National Semiconductor, LMV321M5X Datasheet - Page 14

• Manufacturer Part Number: LMV321M5X
• Description: IC,Operational Amplifier,SINGLE,BICMOS,TSOP,5PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LMV321M5X

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Notes
The values of C
As a design example:
Require: A
Start by selecting C1 and C2. Choose a standard value that
is close to
From Equations (6), (7), (9), (10) ,
The above resistor values are normalized values with
cut-off frequency and resistances to the real values, two
scaling factors are introduced, frequency scaling factor (k
and impedance scaling factor (k
Scaled values:
n
=1rad/s and C
LP
= 2, Q = 1, fc = 1KHz
1
1
and C
= C
R
R
C
2
3
1
2
= R
= R
= C
2
= C
are normally close to or equal to
R
R
R
R
1
4
1
2
3
4
2
n
= 1
= 1
= 4
= 4
= 15.9 k
= 63.6 k
= 0.01 µF
= 1F. To scale the normalized
(Continued)
m
).
FIGURE 15. State Variable Active Filter
(10)
f
)
14
An adjustment to the scaling may be made in order to have
realistic values for resistors and capacitors. The actual value
used for each component is shown in the circuit.
4.4.3 2nd-order High Pass Filter
A 2nd-order high pass filter can be built by simply inter-
changing those frequency selective components (R
C
shown in Figure 14 , resistors become capacitors, and ca-
pacitors become resistors. The resulted high pass filter has
the same corner frequency and the same maximum gain as
the previous 2nd-order low pass filter if the same compo-
nents are chosen.
4.4.4 State Variable Filter
A state variable filter requires three op amps. One conve-
nient way to build state variable filters is with a quad op amp,
such as the LMV324 ( Figure 15 ).
This circuit can simultaneously represent a low-pass filter,
high-pass filter, and bandpass filter at three different outputs.
The equations for these functions are listed below. It is also
called Bi-Quad active filter as it can produce a transfer
function which is quadratic in both numerator and
denominator.
1
FIGURE 14. Sallen-Key 2nd-Order Active High-Pass
, C
2
) in the Sallen-Key 2nd-order active low pass filter. As
Filter
DS100060-39
DS100060-83
1
, R
2
,