OPA277 datasheet(17/43 Pages) TI2

17 / 43 page

Table 7-1 shows the EMIRR IN+ values for the OPA277 at particular frequencies commonly encountered in

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

frequency shown. This information is 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. OPA277 EMIRR IN+ for Frequencies of Interest

FREQUENCY

APPLICATION/ALLOCATION

EMIRR IN+

400 MHz

Mobile radio, mobile satellite-space operation, weather, radar, UHF

59.1 dB

900 MHz

GSM, radio com-nav-GPS (to 1.6 GHz), ISM, aeronautical mobile, UHF

77.9 dB

1.8 GHz

GSM, mobile personal comm. broadband, satellite, L-band

91.3 dB

2.4 GHz

802.11b/g/n, Bluetooth®, mobile personal comm, ISM, amateur radio-satellite, S-band

93.3 dB

3.6 GHz

Radiolocation, aero comm-nav, satellite, mobile, S-band

105.9 dB

5.0 GHz

802.11a/n, aero comm-nav, mobile comm, space-satellite operation, C-band

107.5 dB

7.3.5.1 EMIRR IN+ Test Configuration

Figure 7-5 shows the circuit configuration for testing the EMIRR IN+. An RF source is connected to the

operational amplifier noninverting input terminal using a transmission line. The operational amplifier 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 operational amplifier 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 can

interfere with multimeter accuracy. See the EMI Rejection Ratio of Operational Amplifiers application note for

more details.

Low-Pass Filter

Digital Multimeter

Ambient temperature: 25Û&

Sample /

Averaging

+VS

-VS

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 7-5. EMIRR IN+ Test Configuration Schematic

7.4 Device Functional Modes

The OPAx277 has a single functional mode and is operational when the power-supply voltage is greater than 4 V

(±2 V). The maximum power supply voltage for the OPAx277 is 36 V (±18 V).

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OPA277, OPA2277, OPA4277

SBOS079C – MARCH 1999 – REVISED FEBRUARY 2023

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