+

±

LM7301

Output

Snubber

Network

CC

100 pF

RC

100

Ÿ

Copyright © 2016, Texas Instruments Incorporated

V

+

OUT

VHZ

Ccomp

V

-

-

+

Copyright © 2016, Texas Instruments Incorporated

14

LM7301

SNOS879I – AUGUST 1999 – REVISED MAY 2016

www.ti.com

Product Folder Links: LM7301

Submit Documentation Feedback

Copyright © 1999–2016, Texas Instruments Incorporated

Feature Description (continued)

7.2.5 Low-Distortion, High-Output Drive Capability

The LM7301 offers superior low-distortion performance, with a total-harmonic-distortion-plus-noise of 0.06% at f

= 10 kHz. The advantage offered by the LM7301 is its low distortion levels, even at high output current and low

load resistance. See Stability Considerations for methods used to ensure stability under all load conditions.

7.3 Device Functional Modes

7.3.1 Stability Considerations

Rail-to-rail output amplifiers like the LM7301 use the collector of the drive transistor(s) at the output pin, as

shown in Figure 25. This allows the load to be driven as close as possible towards either supply rail.

Figure 25. Simplified Output Stage Block Diagram

While this architecture maximizes the load voltage swing range, it increases the dependence of loop gain and

subsequently stability, on load impedance and DC load current, compared to a non-rail-to-rail architecture. Thus,

with this type of output stage, it is even more crucial to ensure stability by meticulous bench verification under all

load conditions, and to apply the necessary compensation or circuit modifications to overcome any instability, if

necessary. Any such bench verification should also include temperature, supply voltage, input common mode

and output bias point variations as well as capacitive loading.

For example, one set of conditions for which stability of the LM7301 amplifier may be compromised is when the

DC output load is larger than ±0.5 mA, with input and output biased to mid-rail. Under such conditions, it may be

possible to observe open-loop gain response peaking at a high frequency (for example, 200 MHz), which is

beyond the expected frequency range of the LM7301 (4 MHz GBW). Without taking any precautions against gain

peaking, it is possible to see increased settling time or even oscillations, especially with low closed loop gain and

/ or light AC loading. It is possible to reduce or eliminate this gain peaking by using external compensation

components. One possible scheme that can be applied to reduce or eliminate this gain peaking is shown in

Figure 26.

Figure 26. Non-Dissipating Snubber Network to Reduce Gain Peaking