7.3 Feature Description

7.3.1 Low Operating Voltage

to 5.5 V (±2.75 V). The offset voltage is trimmed at 5.0 V, however, the device maintains ultra-low offset voltages

Key parameters that vary over the supply voltage or temperature range are shown in the Typical Characteristics.

7.3.2 Low Input Bias Current

The typical input bias current of the OPAx397 is extremely low (typically 10 fA). Input bias current is dominated

by leakage current from the ESD protection diodes, which is proportional to the area of the diode. The OPAx397

is able to achieve ultra-low input bias current as a result of modern process technology and advanced ESD

protection design that minimizes the area of the diode.

In overdriven conditions, the bias current can increase significantly. The most common cause of an overdriven

condition occurs when the operational amplifier is outside of the linear range of operation. When the output of

the operational amplifier is driven to one of the supply rails, the feedback loop requirements cannot be satisfied

and a differential input voltage develops across the input pins. This differential input voltage results in the

forward-biasing of the ESD cells. The equivalent circuit is shown in Figure 7-1.

+

±

CORE

10

10

+IN

±IN

V+

V±

Figure 7-1. Equivalent Input Circuit

7.4 Device Functional Modes

The OPAx397 family is operational when the power-supply voltage is greater than 1.7 V (±0.85 V). For devices

that use the EN function (see Section 5), the devices are disabled when the EN pin is low. In this state,

quiescient current is significantly reduced, and the output is high impedance. The maximum specified power-

supply voltage for the OPAx397 is 5.5 V (±2.75 V).

OPA397

SBOSA02 – AUGUST 2021

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