7.2.1.2 Detailed Design Procedure

The linear range of the output stage is limited in how close the output voltage can approach ground under

zero input conditions. In unidirectional applications where measuring very-low input currents is desirable, bias

the REF pin to a convenient value above 50 mV to get the output into the linear range of the device. To limit

common-mode rejection errors, TI recommends buffering the reference voltage connected to the REF pin.

A less frequently-used output biasing method is to connect the REF pin to the supply voltage, V+. This method

results in the output voltage saturating at 200 mV below the supply voltage when no differential input signal is

present. This method is similar to the output-saturated low condition with no input signal when the REF pin is

connected to ground. The output voltage in this configuration only responds to negative currents that develop

negative differential input voltage relative to the device IN– pin. Under these conditions, when the differential

input signal increases negatively, the output voltage moves downward from the saturated supply voltage. The

voltage applied to the REF pin must not exceed the device supply voltage.

7.2.1.3 Application Curve

Figure 7-2 shows an example output response of a unidirectional configuration. With the REF pin connected

directly to ground, the output voltage is biased to this zero output level. The output rises above the reference

voltage for positive differential input signals but cannot fall below the reference voltage for negative differential

input signals because of the grounded reference voltage.

Time (500 µs /div)

0 V

V

OUT

V

REF

Figure 7-2. Unidirectional Application Output Response

INA210-Q1, INA211-Q1, INA212-Q1, INA213-Q1, INA214-Q1, INA215-Q1

SBOS475K – MARCH 2009 – REVISED NOVEMBER 2023

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