Datasheet

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SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006
www.ti.com
14
APPLICATION CIRCUITS
Medical ECG Applications
Figure 9 shows the INA321 configured to serve as a
low-cost ECG amplifier, suitable for moderate accuracy
heart-rate applications such as fitness equipment. The
input signals are obtained from the left and right arms of the
patient. The common-mode voltage is set by two 2MΩ
resistors. This potential, through a buffer, provides an
optional right leg drive. Filtering can be modified to suit
application needs by changing the capacitor value of the
output filter.
Low-Power, Single-Supply Data Acquisition
Systems
Refer to Figure 5 to see the INA321 configured to drive an
ADS7818. Functioning at frequencies of up to 500kHz, the
INA321 is ideal for low-power data acquisition.
OPA336
OPA336
OPA336
Right Arm
Left Arm
OPA336
1MΩ
REF
1MΩ
1MΩ
10kΩ
10kΩ
Shield
Drive
390kΩ
10kΩ
2kΩ
2kΩ
1.6nF
0.1µF
100kΩ
100kΩ
Shield
+5V
V
R
V
R
V
R
=+2.5V
2M
Ω
2M
Ω
Right
Leg
V
R
INA321
5
3
2
8
7
6
4
1
V+
Shutdown
RG
V
IN
−
V−
V
IN
+
V
OUT PUT
100kΩ
Figure 9. Simplified ECG Circuit for Medical Applications