LMH6704MF datasheet(7/12 Pages) NSC

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Application Information

GENERAL INFORMATION

The LMH6704 is a high speed current feedback Selectable

Gain Buffer (SGB), optimized for very high speed and low

distortion. With its internal feedback and gain-setting resis-

tors the LMH6704 offers excellent AC performance while

simplifying board layout and minimizing the affects of layout

related parasitic components. The LMH6704 has no internal

ground reference so single or split supply configurations are

both equally useful.

SETTING THE CLOSED LOOP GAIN

The LMH6704 is a current feedback amplifier with on-chip

F =RG = 465

Ω. As such it can be configured with an A

V =

+2, A

V = +1, or an AV = −1 by connecting pins 3 and 4 as

described in the chart below.

GAIN A

Input Connections

Non-Inverting (Pin 3)

Inverting (Pin 4)

−1 V/V

Ground

Input Signal

+1 V/V

Input Signal

NC (Open)

+2 V/V

Input Signal

Ground

The gain accuracy of the LMH6704 is accurate and guaran-

teed over temperature to within ±1%. The internal gain

setting resistors, R

Fand RG, match very well. The LMH6704

architecture takes advantage of the fact that the internal gain

setting resistors track each other well over a wide range of

temperature and process variation to keep the overall gain

constant, despite the fact that the individual resistors have

nominal temperature drifts. Therefore, using external resis-

tors in series with R

G to change the gain will result in poor

gain accuracy over temperature.

20103603

FIGURE 1. Recommended Gain of +2 Circuit

20103604

FIGURE 2. Recommended Gain of +1 Circuit

20103605

FIGURE 3. Recommended Gain of −1 Circuit

20103609

FIGURE 4. Alternate Unity Gain Configuration

LMH6704MF Datasheet(PDF) 7 Page - National Semiconductor (TI)

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