7.4 Device Functional Modes

7.4.1 Split-Supply Operation (+4/–2 V to ±6.5 V)

In typical split-supply operation, the midpoint between the power rails is ground. The midpoint at ground in a

split-supply configuration is a valid operating condition for the OPA818 when using symmetric supply voltages

that are greater than or equal to ±4 V. This configuration facilitates interfacing the OPA818 with common lab

equipment that have inputs and outputs referenced to ground, such as signal generators, network analyzers,

oscilloscopes, and spectrum analyzers. However, when using split-supply voltages less than ±4 V, ensure that

the input common-mode range is not violated. Be aware that the typical input common-mode range of the

OPA818 includes VS– and extends up to 3.2 V from VS+. For example, when using ±3 V supplies, ensure

that the input common-mode voltage of the signal is typically 3.2 V from VS+ and 3.6 V from VS+, per the

maximum specified input common-mode range. Ground is not included in the input common-mode range with

±3 V supplies, and results in erroneous operation if the input signal has ground as the midpoint. To prevent this

issue, use +4/–2 V supplies.

7.4.2 Single-Supply Operation (6 V to 13 V)

Many newer systems use single power supply to improve efficiency and reduce the cost of the extra power

supply. The OPA818 is designed for use with split-supply configuration. However, the device is available for

use with a single-supply with no change in performance, as long as the input and output are biased within

the linear operation of the device. To change the circuit from split supply to single supply, level shift all the

voltages to mid-supply using VREF. Give additional consideration to the input common-mode range to not violate

requirements when operating with supplies less than 8 V. One of the advantages of configuring an amplifier for

single-supply operation is that the effects of –PSRR are minimized because the low supply rail is grounded.

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OPA818

SBOS940B – MAY 2019 – REVISED DECEMBER 2025

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Product Folder Links: OPA818