OPA2228P datasheet(21/46 Pages) TI1

21 / 46 page

100kΩ

OUT

OPA227

22pF

10Ω

Device

Under

Test

9.09kΩ

1kΩ

97.6kΩ

40.2kΩ

1 F

0.47 F

22nF

2MΩ

402kΩ

634kΩ

Input from

Device

Under

Test

2MΩ

(OPA227)

226kΩ

178kΩ

0.47 F

10nF

178kΩ

(OPA227)

OUT

OPA227, OPA2227, OPA4227

OPA228, OPA2228, OPA4228

www.ti.com

SBOS110B – MAY 1998 – REVISED JUNE 2015

Feature Description (continued)

Figure 41. 0.1 Hz to 10 Hz Bandpass Filter Used to Test Wideband Noise of the

OPAx22x Series

Figure 42. Noise Test Circuit

Figure 41 shows the 0.1 Hz 10 Hz bandpass filter used to test the noise of the OPA227 and OPA228. The filter

circuit was designed using Texas Instruments’ FilterPro software (available at www.ti.com). Figure 42 shows the

configuration of the OPA227 and OPA228 for noise testing.

7.3.8 EMI Rejection Ratio (EMIRR)

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:

1. Operational amplifier 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 operational amplifier inputs have symmetrical physical layouts and exhibit

nearly matching EMIRR performance.

3. EMIRR is easier to measure on noninverting pins than on other pins because the noninverting input terminal

can be isolated on a printed-circuit-board (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.

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Product Folder Links: OPA227 OPA2227 OPA4227 OPA228 OPA2228 OPA4228

OPA2228P Datasheet(PDF) 21 Page - Texas Instruments

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