AD8226ARMZ-R7 datasheet(23/29 Pages) AD

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AD8226

Data Sheet

Rev. C | Page 22 of 28

INPUT PROTECTION

The AD8226 has very robust inputs and typically does not

need additional input protection. Input voltages can be up to

40 V from the opposite supply rail. For example, with a +5 V

positive supply and a −8 V negative supply, the part can safely

withstand voltages from −35 V to 32 V. Unlike some other

instrumentation amplifiers, the part can handle large differen-

tial input voltages even when the part is in high gain. Figure 16,

Figure 17, Figure 19, and Figure 20 show the behavior of the

part under overvoltage conditions.

The rest of the AD8226 terminals should be kept within the

supplies. All terminals of the AD8226 are protected against ESD.

For applications where the AD8226 encounters voltages beyond

the allowed limits, external current-limiting resistors and low-

leakage diode clamps such as the BAV199L, the FJH1100s, or

the SP720 should be used.

RADIO FREQUENCY INTERFERENCE (RFI)

RF rectification is often a problem when amplifiers are used in

applications having strong RF signals. The disturbance can appear

as a small dc offset voltage. High frequency signals can be filtered

with a low-pass RC network placed at the input of the instru-

mentation amplifier, as shown in Figure 63. The filter limits the

input signal bandwidth according to the following relationship:

)

(

DIFF

uency

FilterFreq





uency

FilterFreq



where CD  10 CC.

AD8226

+VS

+IN

–IN

0.1µF

10µF

0.1µF

REF

VOUT

–VS

10nF

1nF

4.02kΩ

Figure 63. RFI Suppression

CD affects the difference signal and CC affects the common-mode

signal. Values of R and CC should be chosen to minimize RFI.

Mismatch between the R × CC at the positive input and the R × CC

at the negative input degrades the CMRR of the AD8226. By using

a value of CD that is one magnitude larger than CC, the effect of

the mismatch is reduced and performance is improved.

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