®

INA2141

10

INPUT PROTECTION

The inputs of the INA2141 are individually protected for

voltages up to

±40V. For example, a condition of –40V on

one input and +40V on the other input will not cause

damage. Internal circuitry on each input provides low series

impedance under normal signal conditions. To provide

equivalent protection, series input resistors would contribute

excessive noise. If the input is overloaded, the protection

circuitry limits the input current to a safe value of approxi-

mately 1.5 to 5mA. The typical performance curve “Input

Bias Current vs Common-Mode Input Voltage” shows this

input current limit behavior. The inputs are protected even if

the power supplies are disconnected or turned off.

CHANNEL CROSSTALK

The two channels of the INA2141 are completely indepen-

dent, including all bias circuitry. At DC and low frequency

there is virtually no signal coupling between channels.

Crosstalk increases with frequency and is dependent on

circuit gain, source impedance and signal characteristics.

As source impedance increases, careful circuit layout will

help achieve lowest channel crosstalk. Most crossstalk is

produced by capacitive coupling of signals from one channel

to the input section of the other channel. To minimize

coupling, separate the input traces as far as practical from

any signals associated with the opposite channel. A grounded

guard trace surrounding the inputs helps reduce stray cou-

pling between channels. Run the differential inputs of each

channel parallel to each other or directly adjacent on top and

bottom side of a circuit board. Stray coupling then tends to

produce a common-mode signal which is rejected by the

IA’s input.

FIGURE 6. ECG Amplifier With Right-Leg Drive.

FIGURE 4. Two-Axis Bridge Amplifier.

FIGURE 5. Sum of Differences Amplifier.

X-axis

V

O

Y-axis

V

O

X-axis

Y-axis

V

EX

V

EX

INA2141

1/2

INA2141

1/2

V

V

1

V

2

Ref

V

3

V

4

Ref

INA2141

1/2

INA2141

1/2

INA2141

1/2

V

O

LA

RL

RA

10k

Ω

Ref

G = 10

20k

Ω

20k

Ω

V

G

1/4

OPA4131

390k

Ω

390k

Ω

1/4

OPA4131

OPA4131

1/4

OPA4131

1/4