OPA227 Datasheet, PDF (22/46 Pages) Burr-Brown (TI) – High Precision, Low Noise OPERATIONAL AMPLIFIERS

OPA227, OPA2227, OPA4227
OPA228, OPA2228, OPA4228
SBOS110B – MAY 1998 – REVISED JUNE 2015
www.ti.com
Feature Description (continued)
A more formal discussion of the EMIRR IN+ definition and test method is provided in application report
SBOA128, EMI Rejection Ratio of Operational Amplifiers, available for download at www.ti.com. The EMIRR IN+
of the OPA227 is plotted versus frequency as shown in Figure 43.
120
P_RF = -10 dbm
V_S = H2.5 V
100 _{VCM = 0 V}
80
60
40
20
0
10
100
1k
10k
Frequency (MHz)
Figure 43. OPA227 EMIRR IN+ vs Frequency
If available, any dual and quad operational amplifier device versions have nearly similar EMIRR IN+
performance. The OPAx227 unity-gain bandwidth is 8 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 OPA227 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
400 MHz
900 MHz
1.8 GHz
2.4 GHz
3.6 GHz
5 GHz
Table 1. OPAx227 EMIRR IN+ for Frequencies of Interest
APPLICATION/ALLOCATION
Mobile radio, mobile satellite/space operation, weather, radar, UHF
GSM, radio com/nav./GPS (to 1.6 GHz), ISM, aeronautical mobile,
UHF
GSM, mobile personal comm. broadband, satellite, L-band
802.11b/g/n, Bluetooth™, mobile personal comm., ISM, amateur
radio/satellite, S-band
Radiolocation, aero comm./nav., satellite, mobile, S-band
802.11a/n, aero comm./nav., mobile comm., space/satellite
operation, C-band
EMIRR IN+
35.7 dB
47.8 dB
68.8 dB
69.8 dB
78 dB
88.4 dB
7.3.8.1 EMIRR IN+ Test Configuration
Figure 44 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 may
interfere with multimeter accuracy. Refer to SBOA128 for more details.
22
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