SBOS377L October 2006 – January 2020 OPA211
The electromagnetic interference (EMI) rejection ratio, or EMIRR, describes the EMI immunity of operational amplifiers. An adverse effect that is common to many operational amplifiers is a change in the offset voltage as a result of RF signal rectification. An operational amplifier that is more efficient at rejecting this change in offset as a result of EMI has a higher EMIRR and is quantified by a decibel value. Measuring EMIRR can be performed in many ways, but this section provides the EMIRR IN+, which specifically describes the EMIRR performance when the RF signal is applied to the noninverting input pin of the operational amplifier. In general, only the noninverting input is tested for EMIRR for the following three reasons:
The EMIRR IN+ of the OPA211 is plotted versus frequency as shown in Figure 46. If available, any dual and quad operational amplifier device versions have nearly similar EMIRR IN+ performance. The OPA211 unity-gain bandwidth is 45 MHz. EMIRR performance below this frequency denotes interfering signals that fall within the operational amplifier bandwidth.
Table 1 shows the EMIRR IN+ values for the OPA211 at particular frequencies commonly encountered in real-world applications. Applications listed in Table 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.
|FREQUENCY||APPLICATION OR ALLOCATION||EMIRR IN+|
|400 MHz||Mobile radio, mobile satellite, space operation, weather, radar, ultra-high frequency (UHF) applications||48.4 dB|
|900 MHz||Global system for mobile communications (GSM) applications, radio communication, navigation, GPS (to 1.6 GHz), GSM, aeronautical mobile, UHF applications||34.6 dB|
|1.8 GHz||GSM applications, mobile personal communications, broadband, satellite, L-band (1 GHz to 2 GHz)||46 dB|
|2.4 GHz||802.11b, 802.11g, 802.11n, Bluetooth®, mobile personal communications, industrial, scientific and medical (ISM) radio band, amateur radio and satellite, S-band (2 GHz to 4 GHz)||56.9 dB|
|3.6 GHz||Radiolocation, aero communication and navigation, satellite, mobile, S-band||61.5 dB|
|5 GHz||802.11a, 802.11n, aero communication and navigation, mobile communication, space and satellite operation, C-band (4 GHz to 8 GHz)||76.7 dB|