LMH6704_14 Datasheet, PDF (8/20 Pages) National Semiconductor (TI) – MHz Selectable Gain Buffer with Disable

LMH6704
SNOSAD0C – FEBRUARY 2005 – REVISED MARCH 2013
APPLICATION INFORMATION
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+5V _{6.8 µF}
.01 µF
V_IN
R_IN
C_SS
0.1 µF
3
6 ^CPOS
+
1
LMH6704
-
4 ₂ C_NEG
.01 µF
V_OUT
V_IN
R_IN
+5V _{6.8 µF}
.01 µF
C_SS
0.1 µF
NC
3
6 ^CPOS
+
1
LMH6704
-
4 ₂ CNEG
.01 µF
V_OUT
6.8 µF
-5V
Figure 17. Recommended Gain of +2 Circuit
6.8 µF
-5V
Figure 18. Recommended Gain of +1 Circuit
+5V _{6.8 µF}
.01 µF
C_SS
0.1 µF
V_IN
R_IN
3
6
+
C_POS
1
LMH6704
-
4 ₂ CNEG
.01 µF
V_OUT
6.8 µF
-5V
Figure 19. Recommended Gain of −1 Circuit
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 resistors 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 R_F = R_G = 465Ω. 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 Table 1.
GAIN A_V
−1 V/V
+1 V/V
+2 V/V
Table 1.
Non-Inverting (Pin 3, SOT-23)
Ground
Input Signal
Input Signal
Input Connections
Inverting (Pin 4, SOT-23)
Input Signal
NC (Open)
Ground
The gain accuracy of the LMH6704 is accurate over temperature to within ±1%. The internal gain setting
resistors, R_Fand R_G, 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 resistors in series with R_G to change the gain will result in poor gain accuracy over temperature.
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