OPA388 Datasheet, PDF (16/32 Pages) Texas Instruments – Precision, Zero-Drift, Zero-Crossover, True Rail-to-Rail Input/Output, Operational Amplifiers

OPA388, OPA2388, OPA4388
SBOS777 – DECEMBER 2016
www.ti.com
Feature Description (continued)
7.3.2 Input Voltage and Zero-Crossover Functionality
The OPAx388 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 37 and Figure 38 contrast the
performance of a traditional complementary rail-to-rail input stage amplifier with the performance of the zero-
crossover OPA388. Significant harmonic content and distortion is generated during the differential pair transition
(such a transition does not exist in the OPA388). Crossover distortion is eliminated through the use of a single
differential pair coupled with an internal low-noise charge pump. The OPAx388 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
Complementary Input Stage
15
OPA388 Zero-Crossover Input Stage
10
5
0
±5
±10
V_CM = ±2.85 V
±15
V_CM = 2.85 V
±20
±3
±2
±1
0
1
2
3
Input Common-mode Voltage (V)
C003
Figure 37. Input Crossover Distortion Nonlinearity
0
±20
±40
±60
Traditional Rail-to-Rail
±80 ^{Input Stage}
±100
±120
OPA388 Zero-Crossover Input Stage
±140
10
100
1k
Frequency (Hz)
10k
C004
Figure 38. Input Crossover Distortion Spectral Content
16
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