Datasheet

V
S+
CM
V
IN
From
source
V
S–
49.9 W
0.22 Fm
R
F
R
F
R
G
R
G
R
IT
R
IT
V
OUT+
V
OUT–
To
50-W
Test
Equipment
R
CMT
R
CM
THS4509
50-W
49.9 W
0.22 Fm
49.9 W
49.9 W
From
50 Ω
Source
THS4509
CM
V
IN
CMRR
PSRR+
PSRR−
V
S+
V
S−
V
S+
V
S−
100 Ω
100 Ω
69.8 Ω
348 Ω
348 Ω
49.9 Ω
49.9 Ω
Open
0.22 µF
100 Ω
Output
Measured
Here
With High
Impedance
Differential
Probe
THS 4509
CM
V
IN
R
F
R
F
R
G
R
G
R
IT
R
IT
From
50 Ω
Source
0.22 µF
49.9 Ω
V
OUT+
Open
To 50 Ω
Test
Equipment
V
S+
V
S−
0.22 µF
V
OUT−
49.9 Ω
49.9 Ω
THS4509
www.ti.com SLOS454H –JANUARY 2005–REVISED NOVEMBER 2009
CM Input
A signal generator is used as the signal source and
the output is measured with a spectrum analyzer. The
The circuit shown in Figure 79 is used to measure the
output impedance of the signal generator is 50 Ω. R
IT
frequency response and input impedance of the CM
and R
G
are chosen to impedance-match to 50 Ω, and
input. Frequency response is measured single-ended
to maintain the proper gain. To balance the amplifier,
at V
OUT+
or V
OUT–
with the input injected at V
IN
, R
CM
=
a 0.22-μF capacitor and 49.9-Ω resistor to ground are
0 Ω, and R
CMT
= 49.9 Ω. The input impedance is
inserted across R
IT
on the alternate input.
measured with R
CM
= 49.9 Ω with R
CMT
= open, and
calculated by measuring the voltage drop across R
CM
A low-pass filter is inserted in series with the input to
to determine the input current.
reduce harmonics generated at the signal source.
The level of the fundamental is measured, then a
high-pass filter is inserted at the output to reduce the
fundamental so that it does not generate distortion in
the input of the spectrum analyzer.
The transformer used in the output to convert the
signal from differential to single-ended is an
ADT1-1WT. It limits the frequency response of the
circuit so that measurements cannot be made below
approximately 1 MHz.
The 1-dB compression point is measured with a
spectrum analyzer with 50-Ω double termination or
100-Ω termination; see Table 2. The input power is Figure 79. CM Input Test Circuit
increased until the output is 1 dB lower than
expected. The number reported in the table data is
CMRR and PSRR
the power delivered to the spectrum analyzer input.
Add 3 dB to refer to the amplifier output.
The circuit shown in Figure 80 is used to measure the
CMRR and PSRR of V
S+
and V
S–
. The input is
S-Parameter, Slew Rate, Transient Response,
switched appropriately to match the test being
Settling Time, Output Impedance, Overdrive,
performed.
Output Voltage, and Turn-On/Off Time
The circuit shown in Figure 78 is used to measure
s-parameters, slew rate, transient response, settling
time, output impedance, overdrive recovery, output
voltage swing, and turn-on/turn-off times of the
amplifier. For output impedance, the signal is injected
at V
OUT
with V
IN
left open and the drop across the
49.9-Ω resistor is used to calculate the impedance
seen looking into the amplifier output.
Because S
21
is measured single-ended at the load
Figure 80. CMRR and PSRR Test Circuit
with 50-Ω double termination, add 12 dB to refer to
the amplifier output as a differential signal.
Figure 78. S-Parameter, SR, Transient Response,
Settling Time, Z
O
, Overdrive Recovery, V
OUT
Swing, and Turn-On/Off Test Circuit
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