Datasheet

THS452x
R
G
R
G
R
IT
R
IT
24.9 W
953 W
1kW
1kW
49.9 W
24.9 W
V
OCM
V
IN+
PD
Measurewith
Differential
Probe
AcrossR
OT
Installedto
Balance
Amplifier
Calibrated
Differential
Probe
Across
R
IT
Open
Open
From
50-
Source
W
V
S+
V
S-
0.22 Fm
0.22 Fm
THS4521
THS4522
THS4524
SBOS458F –DECEMBER 2008–REVISED SEPTEMBER 2011 www.ti.com
TEST CIRCUITS
Table 2. Load Component Values For 1:1
Overview
Differential to Single-Ended Output Transformer
(1)
The THS4521, THS4522, and THS4524 family is
R
L
R
O
R
OT
Atten
tested with the test circuits shown in this section; all
100 Ω 24.9 Ω Open 6 dB
circuits are built using the available THS4521
200 Ω 86.6 Ω 69.8 Ω 16.8 dB
evaluation module (EVM). For simplicity,
power-supply decoupling is not shown; see the layout
499 Ω 237 Ω 56.2 Ω 25.5 dB
in the Applications section for recommendations.
1 kΩ 487 Ω 52.3 Ω 31.8 dB
Depending on the test conditions, component values
1. Total load includes 50-Ω termination by the test
change in accordance with Table 1 and Table 2, or
equipment. Components are chosen to achieve
as otherwise noted. In some cases the signal
load and 50-Ω line termination through a 1:1
generators used are ac-coupled and in others they
transformer.
dc-coupled 50-Ω sources. To balance the amplifier
when ac-coupled, a 0.22-μF capacitor and 49.9-Ω
Frequency Response
resistor to ground are inserted across R
IT
on the
alternate input; when dc-coupled, only the 49.9-Ω
The circuit shown in Figure 53 is used to measure the
resistor to ground is added across R
IT
. A split power
frequency response of the circuit.
supply is used to ease the interface to common test
An HP network analyzer is used as the signal source
equipment, but the amplifier can be operated in a
and the measurement device. The output impedance
single-supply configuration as described in the
of the HP network analyzer is is dc-coupled and is
Applications section with no impact on performance.
50 Ω. R
IT
and R
G
are chosen to impedance-match to
Also, for most of the tests, except as noted, the
50 Ω and maintain the proper gain. To balance the
devices are tested with single-ended inputs and a
amplifier, a 49.9-Ω resistor to ground is inserted
transformer on the output to convert the differential
across R
IT
on the alternate input.
output to single-ended because common lab test
equipment has single-ended inputs and outputs.
The output is probed using a Tektronix
Similar or better performance can be expected with
high-impedance differential probe across the 953-Ω
differential inputs and outputs.
resistor and referred to the amplifier output by adding
back the 0.42-dB because of the voltage divider on
As a result of the voltage divider on the output formed
the output.
by the load component values, the amplifier output is
attenuated. The Atten column in Table 2 shows the
attenuation expected from the resistor divider. When
using a transformer at the output (as shown in
Figure 54), the signal sees slightly more loss because
of transformer and line loss; these numbers are
approximate.
Table 1. Gain Component Values for
Single-Ended Input
(1)
Gain R
F
R
G
R
IT
1 V/V 1 kΩ 1 kΩ 52.3 Ω
2 V/V 1 kΩ 487 Ω 53.6 Ω
5 V/V 1 kΩ 187 Ω 59.0 Ω
10 V/V 1 kΩ 86.6 Ω 69.8 Ω
Figure 53. Frequency Response Test Circuit
1. Gain setting includes 50-Ω source impedance.
Components are chosen to achieve gain and
50-Ω input termination.
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Product Folder Link(s): THS4521 THS4522 THS4524