200 Ps/DIV

+

-

LPV521

SNOSB14C – AUGUST 2009 – REVISED FEBRUARY 2013

www.ti.com

Figure 66. Resistive Isolation of Capacitive Load

chosen to achieve similar dampening at their respective capacitive loads. Notice that for the LPV521 with larger

response. For capacitive loads of 20 pF and below no isolation resistor is needed.

0 – 20 pF

not needed

50 pF

154 k

Ω

100 pF

118 k

Ω

500 pF

52.3 k

Ω

1 nF

33.2 k

Ω

5 nF

17.4 k

Ω

10 nF

13.3 k

Ω

Figure 67. Step Response

EMI SUPPRESSION

The near-ubiquity of cellular, bluetooth, and Wi-Fi signals and the rapid rise of sensing systems incorporating

wireless radios make electromagnetic interference (EMI) an evermore important design consideration for

precision signal paths. Though RF signals lie outside the op amp band, RF carrier switching can modulate the

DC offset of the op amp. Also some common RF modulation schemes can induce down-converted components.

The added DC offset and the induced signals are amplified with the signal of interest and thus corrupt the

measurement. The LPV521 uses on chip filters to reject these unwanted RF signals at the inputs and power

supply pins; thereby preserving the integrity of the precision signal path.

22

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