7.1.2 Transfer Function

Most applications use the INA117 as a simple unity-gain difference amplifier. The transfer function is:

V0 = V3 – V2

V3 and V2 are the voltages at pins 3 and 2.

Figure 7-2. Offset Voltage Trim Circuits

Some applications, however, apply voltages to the reference terminals (pins 1 and 5). A more complete transfer

function is:

V0 = V3 – V2 + 19 × V5 – 18 × V1

V5 and V1 are the voltages at pins 5 and 1.

7.1.3 Measuring Current

The INA117 can be used to measure a current by sensing the voltage drop across a series resistor, RS. Figure

7-4 shows the INA117 used to measure the supply currents of a device under test. The circuit in Figure 7-5

measures the output current of a power supply. If the power supply has a sense connection, the power supply

can be connected to the output side of RS to eliminate the voltage-drop error. Another common application is

current-to-voltage conversion, as shown in Figure 7-6.

INA117

SBOS154B – SEPTEMBER 2000 – REVISED APRIL 2024

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