Reference

Current

V+

V

IN-

V

IN+

V

(Ground)

-

V

BIAS2

V

BIAS1

Class AB

Control

Circuitry

V

O

OPA313

OPA2313

OPA4313

SBOS649C – SEPTEMBER 2012 – REVISED MARCH 2013

www.ti.com

APPLICATION INFORMATION

The OPA313 is a family of low-power, rail-to-rail input and 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

OPA313 family 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 OPA313 features 1-MHz bandwidth and 0.5-V/

μs slew rate with only 50-μA supply current per channel,

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

input noise voltage of 25 nV/

√Hz at 1 kHz, low input bias current (0.2 pA), and an input offset voltage of 0.5 mV

(typical). The typical offset voltage drift is 2

μV/°C; over the full temperature range the input offset voltage

changes only 200

μV (0.5 mV to 0.7 mV).

OPERATING VOLTAGE

The OPA313 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 OPA313 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 34. 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 34. Simplified Schematic

16

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Product Folder Links: OPA313 OPA2313 OPA4313