INA128

R

R

V

O

LA

RL

RA

10kΩ

Ref

G = 10

2.8kΩ

V

V

G

G

2.8kΩ

1/2

OPA2131

390kΩ

390kΩ

1/2

OPA2131

NOTE: Due to the INA128’s current-feedback

topology, VG is approximately 0.7V less than

the common-mode input voltage. This DC offset

in this guard potential is satisfactory for many

guarding applications.

INA128

R

G

I

B

R

V

1

IN

+

A

1

I

O

Load

Ref

I

O

V

IN

R

1

G

−

A

I

1

OPA177

± 1.5nA

OPA131

± 50pA

OPA602

± 1pA

OPA128

± 75fA

INA128, INA129

SBOS051C – OCTOBER 1995 – REVISED OCTOBER 2015

www.ti.com

Low Voltage Operation (continued)

Figure 34. Differential Voltage to Current Converter

Figure 35. 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 INA12x devices.

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.

18

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