ADA4530-1ARZ-R7 datasheet(31/52 Pages) AD

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Data Sheet

ADA4530-1

APPLICATIONS INFORMATION

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Rev. C | 31 of 52

Figure 102. Phase Margin vs. Load Capacitance with Various Output Isolating

Resistors

Figure 103. Frequency Response with CL = 1 nF and Various Isolating

Resistors

EMI REJECTION RATIO

Circuit performance is often adversely affected by high frequency

electromagnetic interference (EMI). When the signal strength is low

and transmission lines are long, an op amp must accurately amplify

the input signals. However, all op amp pins—the noninverting input,

inverting input, positive supply, negative supply, and output pins—

are susceptible to EMI signals. These high frequency signals are

coupled into an op amp by various means, such as conduction,

near field radiation, or far field radiation. For example, wires and

PCB traces can act as antennas and pick up high frequency EMI

signals.

Amplifiers do not amplify EMI or RF signals due to their relatively

low bandwidth. However, due to the nonlinearities of the input

devices, op amps can rectify these out of band signals. When these

high frequency signals are rectified, they appear as a dc offset at

the output.

To describe the ability of the ADA4530-1 to perform as intended in

the presence of electromagnetic energy, the electromagnetic inter-

ference rejection ratio (EMIRR) of the noninverting pin is specified

in Table 1, Table 2, and Table 3 of the Specifications section. A

mathematical method of measuring EMIRR is defined as follows:

EMIRR = 20log(VIN_PEAK/ΔVOS)

(1)

where VIN_PEAK is the peak amplitude of the input voltage.

Figure 104 shows the typical EMIRR vs. frequency performance for

each of the specified supply voltages.

Figure 104. EMIRR vs. Frequency

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