THS4513 Datasheet, PDF (24/34 Pages) Texas Instruments – WIDEBAND, LOW NOISE, LOW DISTORTION FULLY DIFFERENTIAL AMPLIFIER

THS4513
SLOS472 – AUGUST 2005
100-Ω termination as shown in Table 2. The input
power is increased until the output is 1 dB lower than
expected. The number reported in the table data is
the power delivered to the spectrum analyzer input.
Add 3 dB to refer to the amplifier output.
S-Parameter, Slew Rate, Transient Response, Set-
tling Time, Output Impedance, Overdrive, Output
Voltage, and Turn-On/Off Time
The circuit shown in Figure 73 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 ampli-
fier. 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’s output.
Because S₂₁ is measured single-ended at the load
with 50-Ω double termination, add 12 dB to refer to
the amplifier’s output as a differential signal.
From ^VIN
50 Ω
Source
RG
R IT
0.22 µF
49.9 Ω
RG
R IT
RF
V_S+
THS 4513
CM
V_S−
RF
49.9 Ω
49.9 Ω
Open
0.22 µF
V_OUT+
V_OUT−
To 50 Ω
Test
Equipment
Figure 73. S-Parameter, SR, Transient Response,
Settling Time, Z_O, Overdrive Recovery, V_OUT
Swing, and Turn-on/off Test Circuit
CM Input
The circuit shown in Figure 74 is used to measure the
frequency response and input impedance of the CM
input. Frequency response is measured single-ended
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at V_OUT+ or V_OUT– with the input injected at V_IN, R_CM =
0 Ω and R_CMT = 49.9 Ω. The input impedance is
measured with R_CM = 49.9 Ω with R_CMT = open, and
calculated by measuring the voltage drop across R_CM
to determine the input current.
0.22 mF
49.9 W
0.22 mF
49.9 W
R_G
R_IT
R_G
R_IT
R_F
V_S+
49.9 W
THS4513 _{49.9 W}
CM
V_S–
R_F
R_CM
R_CMT
To
V_{OUT– 50-ohm}
Test
V_{OUT+ Equipment}
V_IN From
50-ohm
source
Figure 74. CM Input Test Circuit
CMRR and PSRR
The circuit shown in Figure 75 is used to measure the
CMRR and PSRR of V_S+ and V_S–. The input is
switched appropriately to match the test being per-
formed.
V_S+
PSRR+
From ^VIN
50 Ω
Source
CMRR
PSRR−
V_S−
348 Ω
100 Ω
100 Ω
69.8 Ω
V_S+
THS4513
CM
V_S−
348 Ω
49.9 Ω
49.9 Ω ^{100 Ω}
Open
0.22 µF
Output
Measured
Here
With High
Impedance
Differential
Probe
Figure 75. CMRR and PSRR Test Circuit
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