Datasheet

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:
)2(π2
1
C
D
DIFF
CCR
uencyFilterFreq


C
CM
RC
uencyFilterFreq
π2
1

where
C
D
 10 C
C
.
R
R
AD8226
+
V
S
+IN
–IN
0.1µF
10µF
10µF
0.1µF
REF
V
OUT
–V
S
R
G
C
D
10nF
C
C
1nF
C
C
1nF
4.02kΩ
4.02kΩ
07036-008
Figure 63. RFI Suppression
C
D
affects the difference signal and C
C
affects the common-mode
signal. Values of R and C
C
should be chosen to minimize RFI.
Mismatch between the R × C
C
at the positive input and the R × C
C
at the negative input degrades the CMRR of the AD8226. By using
a value of C
D
that is one magnitude larger than C
C
, the effect of
the mismatch is reduced and performance is improved.