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THS4511 Datasheet, PDF (21/35 Pages) Texas Instruments – WIDEBAND, LOW NOISE, LOW DISTORTION FULLY DIFFERENTIAL AMPLIFIER | |||
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THS4511
www.ti.com
If the signal originates from an ac-coupled 50-â¦
source (see Figure 47), the equivalent dc-source
resistance is an open circuit and RI = RG + RIT.
Table 4 is a modification of Table 1 to add the proper
values with RPD assuming VS+ = 3.75 V, an
ac-coupled 50-⦠source impedance, and setting the
output common-mode voltage to midsupply.
Table 4. RPD Values for Various Gains,
VS+ = 3.75 V, AC-Coupled Signal Source
GAIN
0 dB
RF
348 â¦
RG
340 â¦
RIT
56.2 â¦
RPD
390 â¦
6 dB
348 â¦
169 â¦
64.9 â¦
80.6 â¦
C RS
V Signal
RG
RIT
RPD
RF
VS+ = 3.75 V to 5 V
RG
THS4511
C
RS
RIT
CM
RPD
V S-
RO
V OUT-
RO
V OUT+
RF
Figure 47. THS4511 AC-Coupled Single-Source
Supply Range From 3.75 V to 5 V With RPD Used
To Set VIC
Video Buffer
Figure 48 shows a possible application of the
THS4508 as a dc-coupled video buffer with a gain of
2. Figure 49 shows a plot of the Y' signal originating
from an HDTV 720p video system. The input signal
includes a 3-level sync (minimum level at â0.3 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 â0.3 V below ground. This allows maximum
design flexibility while maintaining a minimum parts
count. Figure 50 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.
SLOS471E â SEPTEMBER 2005 â REVISED NOVEMBER 2009
Video Source
RS = 75 W VIN
175 W
VSignal
130 W
75 W
175 W
130 W
348 W
VS+ = 5 V
THS4511
VS-
VCM = 2.5 V
RO
-
RO VOD
+
348 W
Figure 48. 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 49. 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 50. Video Buffer Differential Output Signal
Copyright © 2005â2009, Texas Instruments Incorporated
Product Folder Link(s): THS4511
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