LMV321M5 datasheet(21/52 Pages) TI1

21 / 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)

9.2.1.3 Application Curves

Figure 55. Frequency Response of Simple Low-Pass Active Filter

Note that the single-op-amp active filters are used in the applications that require low quality factor, Q(

≤ 10), low

frequency (

≤ 5 kHz), and low gain (≤ 10), or a small value for the product of gain times Q (≤ 100). The op amp

should have an open loop voltage gain at the highest frequency of interest at least 50 times larger than the gain

of the filter at this frequency. In addition, the selected op amp should have a slew rate that meets the following

requirement:

Slew Rate

≥ 0.5 × (ω HVOPP) × 10

−6 V/µsec

(1)

where

ωH is the highest frequency of interest, and VOPP is the output peak-to-peak voltage.

9.2.2 Difference Amplifier

The difference amplifier allows the subtraction of two voltages or, as a special case, the cancellation of a signal

common to two inputs. It is useful as a computational amplifier, in making a differential to single-ended

conversion or in rejecting a common mode signal.

Figure 56. Difference Amplifier

9.2.3 Instrumentation Circuits

The input impedance of the previous difference amplifier is set by the resistors R1, R2, R3, and R4. To eliminate

the problems of low input impedance, one way is to use a voltage follower ahead of each input as shown in the

following two instrumentation amplifiers.

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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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