THS3122 Datasheet, PDF (18/43 Pages) Texas Instruments – LOW-NOISE, HIGH-SPEED, 450 mA CURRENT FEEDBACK AMPLIFIERS

THS3122, THS3125
SLOS382E – SEPTEMBER 2001 – REVISED MAY 2015
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
9.1.1 Video Distribution
The wide bandwidth, high slew rate, and high output drive current of the THS3125 and THS3122 match the
demands for video distribution to deliver video signals down multiple cables. To ensure high signal quality with
minimal degradation of performance, a 0.1-dB gain flatness should be at least 7x the passband frequency to
minimize group delay variations from the amplifier. A high slew rate minimizes distortion of the video signal, and
supports component video and RGB video signals that require fast transition times and fast settling times for high
signal quality. Figure 40 illustrates a typical video distribution amplifier application configuration.
470 W
470 W
+15 V
75 W
75-W Transmission Line
V_O(1)
V_I
75 W _{-15 V}
n lines
75 W
75 W
V_O(n)
75 W
Figure 40. Video Distribution Amplifier Application
9.1.2 Driving Capacitive Loads
Applications such as FET drivers and line drivers can be highly capacitive and cause stability problems for high-
speed amplifiers.
Figure 41 through Figure 47 show recommended methods for driving capacitive loads. The basic idea is to use a
resistor or ferrite chip to isolate the phase shift at high frequency caused by the capacitive load from the amplifier
feedback path. See Figure 41 for recommended resistor values versus capacitive load.
60
50
40
30
20
10
0
10
100
C_L - Capacitive Load (pF)
Figure 41. Recommended R_ISO vs Capacitive Load
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