THS3491 Datasheet, PDF (14/28 Pages) Texas Instruments – 900-MHz, High-Power Output, Current Feedback Amplifier

THS3491
SBOS875 – AUGUST 2017
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 THS3491 matches the demands for
video distribution for delivering video signals down multiple cables. For high signal quality with minimal
degradation of performance, use a 0.1-dB gain flatness that is 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.
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Figure 10. Video Distribution Amplifier Application
9.1.2 Driving Capacitive Loads
Applications such as power JFET and MOSFET (powerFET) drivers can be highly capacitive and cause stability
problems for high-speed amplifiers.
Figure 11 and Figure 12 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 Effect of Parasitic Capacitance in Op Amp Circuits for recommended resistor values versus
capacitive load.
1 kΩ
249 Ω
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R_ISO
1 µF
Figure 11. Driving a Large Capacitive Load Using an Output Series Isolation Resistor
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