7.3 Feature Description

7.3.1 Operating Voltage

The OPA3x88 family of operational amplifiers can be used with single or dual supplies from an operating range

device (see Section 6.1). Key parameters that vary over the supply voltage or temperature range are shown in

Section 6.6.

7.3.2 Input Voltage and Zero-Crossover Functionality

The OPA388-Q1 input common-mode voltage range extends 0.1 V beyond the supply rails. This amplifier family

is designed to cover the full range without the troublesome transition region found in some other rail-to-rail

amplifiers. Operating a complementary rail-to-rail input amplifier with signals traversing the transition region

results in unwanted non-linear behavior and polluted spectral content. Figure 7-1 and Figure 7-2 contrast the

performance of a traditional complementary rail-to-rail input stage amplifier with the performance of the zero-

crossover OPA388-Q1. Significant harmonic content and distortion is generated during the differential pair

transition (such a transition does not exist in the OPA388-Q1). Crossover distortion is eliminated through the use

of a single differential pair coupled with an internal low-noise charge pump. The OPA388-Q1 maintains noise,

bandwidth, and offset performance throughout the input common-mode range, thus reducing printed circuit

board (PCB) and bill of materials (BOM) complexity through the reduction of power-supply rails.

±20

±15

±10

±5

0

5

10

15

20

±3

±2

±1

0

1

2

3

Input Common-mode Voltage (V)

Complementary Input Stage

OPA388 Zero-Crossover Input Stage

C003

V

V

Figure 7-1. Input Crossover Distortion Nonlinearity

±140

±120

±100

±80

±60

±40

±20

0

10

100

1k

10k

Frequency (Hz)

C004

Traditional Rail-to-Rail

Input Stage

OPA388 Zero-Crossover Input Stage

Figure 7-2. Input Crossover Distortion Spectral

Content

OPA388-Q1

SBOS989 – AUGUST 2020

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