7 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

7.1 Application Information

Figure 7-1 shows the basic connections required for operation.

Applications with noisy or high-impedance power-supply lines can require decoupling capacitors close to the

device pins.

The output voltage is equal to the differential input voltage between pins 2 and 3. The common mode input

voltage is rejected.

Figure 7-1. Basic Power and Signal Connections

7.1.1 Common-mode Rejection

Common-mode rejection (CMR) of the INA117 is dependent on the input resistor network, which is laser-trimmed

for accurate ratio matching. To maintain high CMR, having low source impedances is important for driving the

two inputs. A 75Ω resistance in series with pin 2 or 3 decreases CMR from 86dB to 72dB.

Resistance in series with the reference pins also degrades CMR. A 4Ω resistance in series with pin 1 or 5

decreases CMRR from 86dB to 72dB.

Most applications do not require trimming. Figure 7-2 and Figure 7-3 show optional circuits that can be used for

trimming offset voltage and common-mode rejection.

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INA117

SBOS154B – SEPTEMBER 2000 – REVISED APRIL 2024

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