LMH6739_07 Datasheet, PDF (8/12 Pages) National Semiconductor (TI) – Very Wideband, Low Distortion Triple Video Buffer

Application Information
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FIGURE 1. Recommended Non-Inverting Gain Circuit,
Gain = +2
GENERAL INFORMATION
The LMH6739 is a high speed current feedback selectable
gain buffer (SGB), optimized for very high speed and low dis-
tortion. With its internal feedback and gain-setting resistors
the LMH6739 offers excellent AC performance while simpli-
fying board layout and minimizing the affects of layout related
parasitic components. The LMH6739 has no internal ground
reference so single or split supply configurations 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
INPUT CONNECTIONS
Non-Inverting
Inverting
−1 V/V
Ground
Input Signal
+1 V/V
Input Signal
NC (Open)
+2 V/V
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 ac-
curacy 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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