LMH6555_14 Datasheet, PDF (17/37 Pages) Texas Instruments – LMH6555 Low Distortion 1.2 GHz Differential Driver

LMH6555
www.ti.com
SNOSAJ1C – NOVEMBER 2006 – REVISED MARCH 2011
2.90
100
2.80
V_OOS
2.70
60
2.60
2.50
20
2.40
GAIN
2.30
-20
2.20
2.10
2.00
R_S1 = 50:
DIFFERENTIAL DRIVE
1.90
-20 -15 -10 -5 0 5
-60
-100
10 15 20
R_{S2 -} R_S1 (:)
Figure 30. Gain & Output Offset Voltage vs. Source Impedance Shift for Differential Input Drive
It is possible to manipulate output offset with little or no effect on source resistance balance, gain, and, cable
termination.
V_X
V_X
R_X
R_S1
+
LMH6555
R_L
V_IN
R_S2
-
100:
R_X
R_S1
+
LMH6555
R_L
V_IN
R_S2
-
100:
(a)
(b)
Figure 31. Differential Output Shift Circuits
R_X, shown in Figure 31(a) and Figure 31(b), injects current into the input to achieve the required output shift. For
a positive shift, positive current would need to be injected into the V_IN+ terminal (Figure 31(a)) and for a negative
shift, to the V_IN^− terminal (Figure 31(b)). Figure 32 shows the effect of R_X on the output with V_X = 3.3V or 5V, and
R_S1 = R_S2 = 50Ω.
1000
V_X = 5V
100
V_X = 3.3V
10
1
0.1
1
10
100
1000
R_X (k:)
Figure 32. LMH6555 Differential Output Shift Due to R_X in Figure 31
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