6 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

6.1 Application Information

6.1.1 Feedback Resistor

4

3

2

7

6

LMH6702

VOUT

+

-

VIN

+5V

-5V

CPOS

6.8µF

RG

RF

.01µF

6.8µF

CNEG

.01µF

RIN

0.1µF

CSS

AV = 1 +RF/RG = VOUT/VIN

Figure 6-1. Recommended Noninverting Gain Circuit

4

3

2

7

6

LMH6702

VOUT

+

-

VIN

+5V

-5V

CPOS

6.8µF

RG

RF

.01µF

6.8µF

CNEG

.01µF

RT

25:

0.1µF

CSS

SELECT RT TO

YIELD DESIRED

RIN = RT||RG

AV =

VOUT

VIN

RF

RG

=

Figure 6-2. Recommended Inverting Gain Circuit

The LMH6702 achieves excellent pulse and distortion performance by using current feedback topology. The

loop gain for a current-feedback op amp, and thus the frequency response, is predominantly set by the

feedback-resistor value. The LMH6702 is optimized for use with a 237Ω feedback resistor. Using lower values

can lead to excessive ringing in the pulse response while a higher value limits the bandwidth. Application Note

OA-13 SNOA366 discusses this configuration in detail along with the occasions where a different RF can be

advantageous.

6.1.2 Harmonic Distortion

The LMH6702 has been optimized for exceptionally low harmonic distortion while driving very demanding

resistive or capacitive loads. Generally, when used as the input amplifier to very high-speed flash ADCs, the

distortions introduced by the converter dominate over the low LMH6702 distortions. Capacitor CSS, shown

across the supplies in Figure 6-1 and Figure 6-2, is critical to achieving the lowest 2nd harmonic distortion.

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LMH6702QML-SP

SNOSAQ2F – JULY 2005 – REVISED AUGUST 2024

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