Datasheet

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 R

and R

is implemented to bias the amplifier so the

input signal is within the input common-mode voltage range of the amplifier. The capacitor C

is placed between

the inverting input and resistor R

to block the DC signal going into the AC signal source, V

. The values of R

and C

affect the cutoff frequency, fc = 1/2πR

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 −R

. 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. R

should be chosen equal to the parallel combination of R

and R

to minimize errors due to bias

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

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