Datasheet

4
3
2
7
6
LMH6703
V
OUT
+
-
V
IN
+5V
-5V
C
POS
6.8 PF
R
G
R
F
0.1 PF
6.8 PF
C
NEG
0.1 PF
R
IN
0.01 PF
C
SS
A
V
= 1 +R
F
/R
G
= V
OUT
/V
IN
4
3
2
7
6
LMH6703
V
OUT
+
-
V
IN
+5V
-5V
C
POS
6.8 PF
R
G
R
F
0.1 PF
6.8 PF
C
NEG
0.1 PF
R
T
25:
0.01 PF
C
SS
SELECT R
T
TO
YIELD DESIRED
R
IN
= R
T
||R
G
A
V
=
V
OUT
V
IN
R
F
R
G
=
LMH6703
SNOSAF2D –FEBRUARY 2005–REVISED MARCH 2013 www.ti.com
APPLICATION INFORMATION
Figure 27. Recommended Non-Inverting Gain Figure 28. Recommended Inverting Gain Circuit
Circuit
(SOIC Pinout Shown)
(SOIC Pinout Shown)
GENERAL DESCRIPTION
The LMH6703 is a high speed current feedback amplifier, optimized for excellent bandwidth, gain flatness, and
low distortion. The loop gain for a current feedback op amp, and hence the frequency response, is predominantly
set by the feedback resistor value. The LMH6703 in the SOT-23-6 package is optimized for use with a 560Ω
feedback resistor. The LMH6703 in the SOIC package is optimized for use with a 390Ω feedback resistor. Using
lower values can lead to excessive ringing in the pulse response while a higher value will limit the bandwidth.
Application Note OA-13 (SNOA366) discusses this in detail along with the occasions where a different R
F
might
be advantageous.
EVALUATION BOARDS
Device Package Evaluation Board Part Number
LMH6703MF SOT-23-6 CLC730216
LMH6703MA SOIC CLC730227
FEEDBACK RESISTOR SELECTION
One of the key benefits of a current feedback operational amplifier is the ability to maintain optimum frequency
response independent of gain by using appropriate values for the feedback resistor (R
F
). The Electrical
Characteristics and Typical Performance plots specify an R
F
of 560Ω (390Ω for the SOIC package), a gain of +2
V/V and ±5V power supplies (unless otherwise specified). Generally, lowering R
F
from it’s recommended value
will peak the frequency response and extend the bandwidth while increasing the value of R
F
will cause the
frequency response to roll off faster. Reducing the value of R
F
too far below it’s recommended value will cause
overshoot, ringing and, eventually, oscillation.
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