1. 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.

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

EMIRR performance.

3. 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

because the amplifier does 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. Make sure to properly shield and isolate sensitive analog nodes

from noisy radio signals, digital clocks, and interfaces.

The EMIRR +IN of the OPA396 is plotted versus frequency as shown in Figure 7-2. The OPA396 unity-gain

bandwidth is 1 MHz. EMIRR performance less than this frequency denotes interfering signals that fall within the

op amp bandwidth.

Frequency (Hz)

0

20

40

60

80

100

120

140

10M

100M

1000M

C007

Figure 7-2. EMIRR Testing

Table 7-1. OPA396 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

39.1 dB

900 MHz

Global system for mobile communications (GSM) applications, radio communication, navigation, GPS

(to 1.6 GHz), GSM, aeronautical mobile, UHF applications

46.5 dB

1.8 GHz

GSM applications, mobile personal communications, broadband, satellite, L-band (1 GHz to 2 GHz)

61.3 dB

2.4 GHz

medical (ISM) radio band, amateur radio and satellite, S-band (2 GHz to 4 GHz)

69.8 dB

3.6 GHz

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

82.5 dB

5 GHz

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

operation, C-band (4 GHz to 8 GHz)

83.6 dB

7.4 Device Functional Modes

The OPA396 has a single functional mode and is operational when the power-supply voltage is greater than

1.7 V (±0.85 V). The maximum specified power-supply voltage for the OPA396 is 5.5 V (±2.75 V).

OPA396

SBOSA65 – JULY 2021

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