Z

LOAD

+

-

V

+

FREQUENCY (Hz)

10

0

-10

-20

-30

-40

1k

10k

100k

FILTER A

FILTER B

COMBINED

FILTER

LMV841, LMV842, LMV844

SNOSAT1G – OCTOBER 2006 – REVISED FEBRUARY 2013

www.ti.com

Figure 41. Active Filter Curve

The responses of filter A and filter B are shown as the thin lines in Figure 41; the response of the combined filter

is shown as the thick line. Shifting the center frequencies of the separate filters farther apart, will result in a wider

band; however, positioning the center frequencies too far apart will result in a less flat gain within the band. For

wider bands more band-pass filters can be cascaded.

Tip: Use the WEBENCH internet tools at www.ti.com for your filter application.

HIGH-SIDE CURRENT SENSING

current sensing applications.

To measure a current, a sense resistor is placed in series with the load, as shown in Figure 42. The current

flowing through this sense resistor will result in a voltage drop, that is amplified by the op amp.

Suppose it is necessary to measure a current between 0A and 2A using a sense resistor of 100m

Ω, and convert

it to an output voltage of 0 to 5V. A current of 2A flowing through the load and the sense resistor will result in a

voltage of 200mV across the sense resistor. The op amp will amplify this 200mV to fit the current range to the

output voltage range. Use the formula:

(20)

low to obtain a good common-mode rejection.

Figure 42. High-Side Current Sensing

22

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