LMV321M7SLASHNOPB datasheet(25/52 Pages) TI1

25 / 52 page

LMV321-N, LMV321-N-Q1, LMV358-N

LMV358-N-Q1, LMV324-N, LMV324-N-Q1

www.ti.com

SNOS012J – AUGUST 2000 – REVISED DECEMBER 2014

Typical Applications (continued)

From Equation 7, Equation 8, Equation 10, and Equation 11,

R1= 1Ω

(15)

R2= 1Ω

(16)

R3= 4Ω

(17)

R4= 4Ω

(18)

The above resistor values are normalized values with

ωn = 1 rad/s and C1 = C2 = Cn = 1F. To scale the

normalized cutoff frequency and resistances to the real values, two scaling factors are introduced, frequency

scaling factor (kf) and impedance scaling factor (km).

(19)

Scaled values:

R2 = R1 = 15.9 kΩ

(20)

R3 = R4 = 63.6 kΩ

(21)

C1 = C2 = 0.01 µF

(22)

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.

9.2.5 2nd-Order High Pass Filter

A 2nd-order high pass filter can be built by simply interchanging those frequency selective components (R1, R2,

C1, C2) in the Sallen-Key 2nd-order active low pass filter. As shown in Figure 61, resistors become capacitors,

and capacitors 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 components are chosen.

Figure 61. Sallen-Key 2nd-Order Active High-Pass Filter

9.2.6 State Variable Filter

A state variable filter requires three op amps. One convenient way to build state variable filters is with a quad op

amp, such as the LMV324 (Figure 62).

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Product Folder Links: LMV321-N LMV321-N-Q1 LMV358-N LMV358-N-Q1 LMV324-N LMV324-N-Q1

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