• Op amp input pins are known to be the most sensitive to EMI, and typically rectify RF signals better than the

supply or output pins.

• The noninverting and inverting op amp inputs have symmetrical physical layouts and exhibit nearly matching

EMIRR performance

• EMIRR is more simple to measure on noninverting pins than on other pins because the noninverting

input terminal can be isolated on a PCB. This isolation allows the RF signal to be applied directly to the

noninverting input terminal with no complex interactions from other components or connecting PCB traces.

High-frequency signals conducted or radiated to any pin of the operational amplifier may result in adverse

effects, as the amplifier would not have sufficient loop gain to correct for signals with spectral content outside the

bandwidth. Conducted or radiated EMI on inputs, power supply, or output may result in unexpected dc offsets,

transient voltages, or other unknown behavior. Take care to properly shield and isolate sensitive analog nodes

from noisy radio signals and digital clocks and interfaces.

The EMIRR +IN of the OPAx182 is plotted versus frequency as shown in Figure 8-2. If available, any dual and

quad op amp device versions have nearly similar EMIRR +IN performance. The OPAx182 gain bandwidth is 5

MHz. EMIRR performance below this frequency denotes interfering signals that fall within the op amp bandwidth.

Frequency (Hz)

20

30

40

50

60

70

80

90

100

110

120

130

140

10M

100M

1G

5G

Figure 8-2. EMIRR Testing

Table 8-1. OPAx182 EMIRR IN+ for Frequencies of Interest

FREQUENCY

APPLICATION AND ALLOCATION

EMIRR IN+

400 MHz

Mobile radio, mobile satellite, space operation, weather, radar, ultra-high frequency

(UHF) applications

44.9 dB

900 MHz

Global system for mobile communications (GSM) applications, radio

communication, navigation, GPS (to 1.6 GHz), GSM, aeronautical mobile, UHF

applications

48.4 dB

1.8 GHz

GSM applications, mobile personal communications, broadband, satellite, L-band

(1 GHz to 2 GHz)

81.7 dB

2.4 GHz

industrial, scientific and medical (ISM) radio band, amateur radio and satellite,

S-band (2 GHz to 4 GHz)

87.9 dB

3.6 GHz

Radiolocation, aero communication and navigation, satellite, mobile, S-band

137.2 dB

5 GHz

802.11a, 802.11n, aero communication and navigation, mobile communication,

space and satellite operation, C-band (4 GHz to 8 GHz)

99.2 dB

OPA182, OPA2182, OPA4182

SBOS936D – DECEMBER 2019 – REVISED DECEMBER 2021

www.ti.com

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