+IN

-IN

+

-

Preamplifier

Gain = 10

Output Buffer

Gain = K2

A1

A2

OFFSET

Internal

Resistor

100 k:

OUT

Level

shift

1

5

3

4

7

8

9

2

4

1

C

1

LMP8602, LMP8602Q, LMP8603, LMP8603Q

www.ti.com

SNOSB36D – JULY 2009 – REVISED MARCH 2013

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Or for a gain = 5:

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and for a gain = 10:

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Note that the frequency response achieved using this procedure will only be accurate if the cut-off frequency of

the second order filter is much smaller than the intrinsic 60 kHz low-pass filter. In other words, to have the

frequency response of the LMP8602/LMP8602Q/LMP8603/LMP8603Q circuit chosen such that the internal poles

do not affect the external second order filter.

For a desired Q = 0.707 and a cut off frequency = 3 kHz, this will result for the LMP8602 in rounded values for

R2 = 51 k

Ω, C1 = 1.5 nF and C2 = 3.9 nF

And for the LMP8603 this will result in rounded values for R2 = 22 k

Ω, C1 = 3.3 nF and C2 = 0.39 nF

GAIN ADJUSTMENT

The gain of the LMP8602 is 50 and the gain of the LMP8603 is 100, however, this gain can be adjusted as the

signal path in between the two internal amplifiers is available on the external pins.

Reduce Gain

Figure 44 shows the configuration that can be used to reduce the gain of the LMP8602 and the LMP8603 in

unidirectional sensing applications.

Figure 44. Reduce Gain for Unidirectional Application

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Product Folder Links: LMP8602 LMP8602Q LMP8603 LMP8603Q