THS4511-SP Datasheet, PDF (17/24 Pages) Texas Instruments – RAD-TOLERANT CLASS V, WIDEBAND, FULLY DIFFERENTIAL AMPLIFIER

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resistance is an open circuit, and R_I = R_G + R_IT.
Table 4 is a modification of Table 1 to add the proper
values with R_PD assuming V_S+ = 3.75 V, an
ac-coupled 50 Ω source impedance, and setting the
output common-mode voltage to mid-supply.
Table 4. R_PD Values for Various Gains,
V_S+ = 3.75 V, AC-Coupled Signal Source
Gain
6 dB
R_F
348 Ω
R_G
169 Ω
R_IT
64.9 Ω
R_PD
86.6 Ω
10 dB
348 Ω
102 Ω
78.7 Ω
110 Ω
14 dB
348 Ω
61.9 Ω
115 Ω
158 Ω
20 dB
348 Ω
40.2 Ω
221 Ω
226 Ω
C _RS
V _Signal
RG
R_IT
R_PD
RF
V_S+ = 3.75 V to 5 V
R_G
THS4511
C
RS
R_IT
CM
R_PD
V S-
R_O
V _OUT-
R_O
V _OUT+
R_F
Figure 39. THS4511 AC Coupled Single-Source
Supply Range From 3.75 V to 5 V With R_PD Used
to Set V_IC
Video Buffer
Figure 40 shows a possible application of the
THS4511 as a DC-coupled video buffer with a gain
of 2. Figure 41 shows a plot of the Y' signal
originating from a HDTV 720p video system. The
input signal includes a tri-level sync (minimum level at
–0.3 V) and the portion of a video signal with
maximum amplitude of 0.7 V. Although the buffer
draws its power from a 5 V single-ended power
supply, internal level shifters allow the buffer to
support input signals, which are as much as –0.3 V
below ground. This allows maximum design flexibility
while maintaining a minimum parts count. Figure 42
shows the differential output of the buffer. Note that
the DC-coupled amplifier can introduce a DC offset
on a signal applied at its input.
THS4511–SP
SLOS538A – SEPTEMBER 2007 – REVISED OCTOBER 2007
Video Source
R_S = 75 W V_IN
175 W
V_Signal
130 W
75 W
175 W
130 W
348 W
V_S+ = 5 V
THS4511
V_S-
V_CM = 2.5 V
R_O
-
R_O ^VOD
+
348 W
Figure 40. Single-Supply Video Buffer, Gain = 2
0.8
0.6
0.4
0.2
0
-0.2
-0.4
0
5
10
15
20
t - Time - ms
Figure 41. Y' Signal With 3-Level Sync and Video
Signal
1.5
1
0.5
0
-0.5
-1
0
5
10
15
20
t - Time - ms
Figure 42. Video Buffer Differential Output Signal
Copyright © 2007, Texas Instruments Incorporated
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