THS3201-EP_14 Datasheet, PDF (19/34 Pages) Texas Instruments – 1.8-GHz LOW-DISTORTION CURRENT-FEEDBACK AMPLIFIER

THS3201-EP
www.ti.com ..................................................................................................................................................... SGLS283B – APRIL 2005 – REVISED JANUARY 2009
Single Supply Operation
The THS3201 has the capability to operate from a
single-supply voltage ranging from 6.6 V to 15 V.
When operating from a single power supply, care
must be taken to ensure the input signal and amplifier
is biased appropriately to allow for the maximum
output voltage swing. The circuits shown in Figure 58
demonstrate methods to configure an amplifier in a
manner conducive for single-supply operation
+V_S
50 Ω Source
V_I
R_T 49.9 Ω
+
THS3201
_
+V_S
2
R_F
R_G
768 Ω
768 Ω
49.9 Ω
50 Ω
+V_S
2
R_F
50 Ω Source
R_G
V_I
287 Ω
60.4 Ω R_T
+V_S
+V_S
2
2
576 Ω
V_S
_
THS3201
+
49.9 Ω
50 Ω
Figure 58. DC-Coupled Single-Supply Operation
768 Ω
768 Ω
±7.5 V
V_I
THS3201
-
+
±7.5 V
75 Ω
75-Ω Transmission Line
75 Ω
V_O(1)
n Lines
75 Ω
75 Ω
V_O(n)
75 Ω
Figure 59. Video Distribution Amplifier
Application
ADC Driver Application
The THS3201 can be used as a high-performance
ADC driver in applications such as radio receiver IF
stages and test and measurement devices. All
high-performance ADCs have differential inputs. The
THS3201 can be used in conjunction with a
transformer as a drive amplifier in these applications.
Figure 60 and Figure 61 show two different
approaches.
In Figure 60, a transformer is used after the amplifier
to convert the signal to differential. The advantage of
this approach is fewer components are required.
R_OUT and R_T are required for impedance matching
the transformer.
V_S+
Video HDTV Drivers
The exceptional bandwidth and slew rate of the
THS3201 matches the demands for professional
video and HDTV. Most commercial HDTV standards
require a video passband of 30 MHz. 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 requiring 210-MHz 0.1-dB frequency
flatness from the amplifier. High slew rates ensure
there is minimal distortion of the video signal.
Component video and RGB video signals require fast
transition times and fast settling times to keep high
signal quality. The THS8135, for example, is a
240-MSPS video DAC and has a transition time
approaching 4 ns. The THS3201 is a perfect
candidate for interfacing the output of such
high-performance video components.
0.1 µF
R_G
R_F
THS3201
R_OUT 1:n
24.9 Ω
V_IN
R_T 47pF
ADC
24.9 Ω
V_S-
CM
47pF
0.1 µF
0.1 µF
Figure 60. Differential ADC Driver Circuit 1
In Figure 61, a transformer is used before two
amplifiers to convert the signal to differential. The two
amplifiers then amplify the differential signal. The
advantage to this approach is each amplifier is
required to drive one half the voltage as before. R_T is
used to impedance match the transformer.
Copyright © 2005–2009, Texas Instruments Incorporated
Product Folder Link(s): THS3201-EP
Submit Documentation Feedback
19