INA118

SBOS027A – SEPTEMBER 2000 – REVISED JANUARY 2016

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Device Functional Modes (continued)

Low-frequency noise of the INA118 is approximately 0.28 µVp-p, measured from 0.1 to 10 Hz (G

≥100). This

provides dramatically improved noise when compared to state-of-the-art chopper-stabilized amplifiers.

7.4.2 Input Common-Mode Range

The linear input voltage range of the input circuitry of the INA118 is from approximately 0.6-V less than the

positive supply voltage to 1-V greater than the negative supply. As a differential input voltage causes the output

Thus, the linear common-mode input range is related to the output voltage of the complete amplifier. This

behavior also depends on supply voltage; see Figure 6.

Input-overload can produce an output voltage that appears normal. For example, if an input overload condition

drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output

amplifier is near zero. The output of the INA118 is near 0 V even though both inputs are overloaded.

7.4.3 Input Protection

The inputs of the INA118 are individually protected for voltages up to ±40 V. For example, a condition of –40 V

on one input and +40 V on the other input does 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 approximately 1.5 to 5 mA. Figure 12 shows this input current limit behavior. The inputs are protected

even if the power supplies are disconnected or turned off.

12

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