R

IN

TLV379

V

IN

V

OUT

R

F

C

FB

C

IN

10

to

W

20 W

TLV379

V

S

V

IN

V

OUT

R

S

R

L

C

L

13

TLV379, TLV2379, TLV4379

www.ti.com

SBOS785B – APRIL 2016 – REVISED AUGUST 2017

Product Folder Links: TLV379 TLV2379 TLV4379

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Copyright © 2016–2017, Texas Instruments Incorporated

Feature Description (continued)

8.3.3 Rail-to-Rail Output

Designed as a micropower, low-noise operational amplifier, the TLV379 delivers a robust output drive capability.

A class AB output stage with common-source transistors is used to achieve full rail-to-rail output swing capability.

For resistive loads up to 25 kΩ, the output typically swings to within 5 mV of either supply rail, regardless of the

power-supply voltage applied.

8.3.4 Capacitive Load and Stability

Follower configurations with load capacitance in excess of 30 pF can produce extra overshoot (see the typical

characteristic graph, Small-Signal Overshoot vs Capacitive Load, Figure 11) and ringing in the output signal.

Increasing the gain enhances the ability of the amplifier to drive greater capacitive loads. In unity-gain

configurations, capacitive load drive can be improved by inserting a small (10

Ω to 20 Ω) resistor, RS, in series

with the output as shown in Figure 14. This resistor significantly reduces ringing and maintains direct current (dc)

performance for purely capacitive loads. However, if a resistive load is in parallel with the capacitive load, a

voltage divider is created, introducing a dc error at the output and slightly reducing the output swing. The error

introduced is proportional to the ratio of RS / RL and is generally negligible.

Figure 14. Series Resistor in Unity-Gain Buffer Configuration Improves Capacitive Load Drive

In unity-gain inverter configuration, phase margin can be reduced by the reaction between the capacitance at the

operational amplifier (op amp) input and the gain-setting resistors. Best performance is achieved by using

smaller-value resistors. However, when large-value resistors cannot be avoided, a small (4 pF to 6 pF) capacitor

(CFB) can be inserted in the feedback, as shown in Figure 15. This configuration significantly reduces overshoot

by compensating the effect of capacitance (CIN) that includes the amplifier input capacitance (3 pF) and printed

circuit board (PCB) parasitic capacitance.

Figure 15. Improving Stability for Large RF and RIN

8.4 Device Functional Modes

The TLV379 family has a single functional mode. These devices are powered on as long as the power-supply

voltage is between 1.8 V (±0.9 V) and 5.5 V (±2.75 V).