Table 7-1 lists the EMIRR IN+ values for the OPAx145 at particular frequencies commonly encountered in real-

world applications. Applications listed in Table 7-1 may be centered on or operated near the particular frequency

shown. This information may be of special interest to designers working with these types of applications, or

working in other fields likely to encounter RF interference from broad sources, such as the industrial, scientific,

and medical (ISM) radio band.

Table 7-1. OPAx145 EMIRR IN+ for Frequencies of Interest

FREQUENCY

APPLICATION OR ALLOCATION

EMIRR IN+

400 MHz

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

applications

54 dB

900 MHz

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

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

68 dB

1.8 GHz

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

86 dB

2.4 GHz

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

107 dB

3.6 GHz

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

100 dB

5 GHz

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

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

105 dB

7.3.8 EMIRR +IN Test Configuration

Figure 7-6 shows the circuit configuration for testing the EMIRR IN+. An RF source is connected to the op amp

noninverting input terminal using a transmission line. The op amp is configured in a unity-gain buffer topology

with the output connected to a low-pass filter (LPF) and a digital multimeter (DMM). A large impedance

mismatch at the op amp input causes a voltage reflection; however, this effect is characterized and accounted

for when determining the EMIRR IN+. The resulting DC offset voltage is sampled and measured by the

multimeter. The LPF isolates the multimeter from residual RF signals that may interfere with multimeter

accuracy.

+

±

Low-Pass Filter

50

Digital Multimeter

Ambient temperature: 25Û&

Sample /

Averaging

Not shown: 0.1 µF and 10 µF

supply decoupling

RF source

DC Bias: 0 V

Modulation: None (CW)

Frequency Sweep: 201 pt. Log

Figure 7-6. EMIRR +IN Test Configuration

7.4 Device Functional Modes

The OPAx145 has a single functional mode and is operational when the power-supply voltage is greater than 4.5

V (±2.25 V). The maximum power supply voltage for the OPAx145 is 36 V (±18 V).

OPA145,, OPA2145

SBOS427E – JUNE 2017 – REVISED OCTOBER 2020

www.ti.com

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