Bypass

Capacitor

Bypass

Capacitor

Gain Resistor

R

6

V–

IH

V+

IH

V–

R

6

V+

V

O

REF

–

+

V+

V

OUT

GND

V

IN

V

IN

GND

V–

INA129

R

G/2

R = 5.6k

G

W

V

O

LA

RL

RA

10kW

Ref

G = 10

2.8kW

V

V

G

G

2.8kW

1/2

OPA2131

390kW

390kW

1/2

OPA2131

NOTE: Due to the INA129’s current-feedback

topology, VG is approximately 0.7 V less than

the common-mode input voltage. This DC offset

in this guard potential is satisfactory for many

guarding applications.

INA129-EP

SBOS508A – DECEMBER 2009 – REVISED DECEMBER 2015

www.ti.com

Low Voltage Operation (continued)

Figure 27. ECG Amplifier With Right-Leg Drive

10 Layout

10.1 Layout Guidelines

Place the power-supply bypass capacitor as closely as possible to the supply and ground pins. The

recommended value of this bypass capacitor is 0.1

μF to 1 μF. If necessary, additional decoupling capacitance

can be added to compensate for noisy or high-impedance power supplies. These decoupling capacitors must be

placed between the power supply and INA129-EP device.

The gain resistor must be placed close to pin 1 and pin 8. This placement limits the layout loop and minimizes

any noise coupling into the part.

10.2 Layout Example

Figure 28. Recommended Layout

18

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