THS4511 Datasheet, PDF (18/25 Pages) Texas Instruments – WIDEBAND, LOW NOISE, LOW DISTORTION FULLY DIFFERENTIAL AMPLIFIER

THS4511
SLOS471 – SEPTEMBER 2005
Table 4. R_PD Values for Various Gains,
V_S+ = 3.75 V, AC-coupled Signal Source
Gain
0 dB
R_F
348 Ω
R_G
340 Ω
R_IT
56.2 Ω
R_PD
390 Ω
6 dB
348 Ω
169 Ω
64.9 Ω
80.6 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 47. 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 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 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 5V 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 50 shows the differential
output of the buffer. Note that the DC-coupled ampli-
fier can introduce a DC offset on a signal applied at
its input.
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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 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
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