Reference

Current

V+

V

IN-

V

IN+

V

(Ground)

-

V

BIAS2

V

BIAS1

Class AB

Control

Circuitry

V

O

OPA314

OPA2314

OPA4314

SBOS563B

– MAY 2011 – REVISED DECEMBER 2011

www.ti.com

APPLICATION INFORMATION

The OPA314 is a family of low-power, rail-to-rail input/output operational amplifiers specifically designed for

portable applications. These devices operate from 1.8 V to 5.5 V, are unity-gain stable, and suitable for a wide

range of general-purpose applications. The class AB output stage is capable of driving

≤ 10-kΩ loads connected

to any point between V+ and ground. The input common-mode voltage range includes both rails, and allows the

OPA314 series to be used in virtually any single-supply application. Rail-to-rail input and output swing

significantly increases dynamic range, especially in low-supply applications, and makes them ideal for driving

sampling analog-to-digital converters (ADCs).

The OPA314 features 3-MHz bandwidth and 1.5-V/

μs slew rate with only 150-μA supply current per channel,

providing good ac performance at very low power consumption. DC applications are also well served with a very

low input noise voltage of 14 nV/

√Hz at 1 kHz, low input bias current (0.2 pA), and an input offset voltage of

0.5 mV (typical).

Operating Voltage

The OPA314 series op amps are fully specified and ensured for operation from +1.8 V to +5.5 V. In addition,

many specifications apply from

–40°C to +125°C. Parameters that vary significantly with operating voltages or

temperature are shown in the Typical Characteristics graphs. Power-supply pins should be bypassed with

0.01-

μF ceramic capacitors.

Rail-to-Rail Input

The input common-mode voltage range of the OPA314 series extends 200 mV beyond the supply rails. This

performance is achieved with a complementary input stage: an N-channel input differential pair in parallel with a

P-channel differential pair, as shown in Figure 33. The N-channel pair is active for input voltages close to the

positive rail, typically (V+)

– 1.3 V to 200 mV above the positive supply, while the P-channel pair is on for inputs

from 200 mV below the negative supply to approximately (V+)

– 1.3 V. There is a small transition region, typically

(V+)

– 1.4 V to (V+) – 1.2 V, in which both pairs are on. This 200-mV transition region can vary up to 300 mV

with process variation. Thus, the transition region (both stages on) can range from (V+)

– 1.7 V to (V+) – 1.5 V

on the low end, up to (V+)

– 1.1 V to (V+) – 0.9 V on the high end. Within this transition region, PSRR, CMRR,

offset voltage, offset drift, and THD may be degraded compared to device operation outside this region.

Figure 33. Simplified Schematic

14

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© 2011, Texas Instruments Incorporated

Product Folder Link(s): OPA314 OPA2314 OPA4314