LMV321M7SLASHNOPB datasheet(18/44 Pages) TI1

18 / 44 page

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

LMV324-N, LMV324-N-Q1

SNOS012I – AUGUST 2000 – REVISED FEBRUARY 2013

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Figure 57. Two-Op-Amp Instrumentation Amplifier

Single-Supply Inverting Amplifier

There may be cases where the input signal going into the amplifier is negative. Because the amplifier is

operating in single supply voltage, a voltage divider using R3 and R4 is implemented to bias the amplifier so the

input signal is within the input common-mode voltage range of the amplifier. The capacitor C1 is placed between

the inverting input and resistor R1 to block the DC signal going into the AC signal source, VIN. The values of R1

and C1 affect the cutoff frequency, fc = 1/2πR1C1.

As a result, the output signal is centered around mid-supply (if the voltage divider provides V+/2 at the non-

inverting input). The output can swing to both rails, maximizing the signal-to-noise ratio in a low voltage system.

Figure 58. Single-Supply Inverting Amplifier

ACTIVE FILTER

Simple Low-Pass Active Filter

The simple low-pass filter is shown in Figure 59. Its low-frequency gain (

ω → 0) is defined by −R3/R1. This allows

low-frequency gains other than unity to be obtained. The filter has a

−20 dB/decade roll-off after its corner

frequency fc. R2 should be chosen equal to the parallel combination of R1 and R3 to minimize errors due to bias

current. The frequency response of the filter is shown in Figure 60.

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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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