LMH6739 Datasheet, PDF (7/10 Pages) National Semiconductor (TI) – Very Wideband, Low Distortion Triple Video Buffer

Application Section
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FIGURE 1. Recommended Non-Inverting Gain Circuit,
Gain = +2
GENERAL INFORMATION
The LMH6739 is a high speed current feedback Program-
mable Gain Buffer (PGB), optimized for very high speed and
low distortion. With its internal feedback and gain-setting
resistors the LMH6739 offers excellent AC performance
while simplifying board layout and minimizing the affects of
layout related parasitic components. The LMH6739 has no
internal ground reference so single or split supply configura-
tions are both equally useful.
SETTING THE CLOSED LOOP GAIN
The LMH6739 is a current feedback amplifier with on-chip
R_F = R_G = 450Ω. As such it can be configured with an A_V =
+2, A_V = +1, or an A_V = −1 by connecting pins 3 and 4 as
described in the chart below.
GAIN A_V
−1 V/V
+1 V/V
+2 V/V
INPUT CONNECTIONS
Non-Inverting (Pin 3) Inverting (Pin 4)
Ground
Input Signal
Input Signal
NC (Open)
Input Signal
Ground
The gain of the LMH6739 is accurate to ±1% and stable over
temperature. The internal gain setting resistors, R_F and R_G,
match very well. However, over process and temperature
their absolute value will change. Using external resistors in
series with R_G to change the gain will result in poor gain
accuracy over temperature and from part to part.
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FIGURE 2. Recommended Non-Inverting Gain Circuit,
Gain +1
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FIGURE 4. Correction for Unity Gain Peaking
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FIGURE 3. Recommended Inverting Gain Circuit,
Gain = –1
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FIGURE 5. Frequency Response for Circuit in Figure 4
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