Datasheet

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-20
-17
-15
-13
-11
-7
-5
-3
-1
0
1
3
0.1 1 10 100
1000
f-Frequency-MHz
V -SignalGain-dB
OCM
-19
V
R =499
R =200
Gain=0dB
=100mV
V = 1.65V
F
L
PP
S
W
W
O
±
2
-2
-4
-6
-9
-8
-10
-12
-14
-16
-18
TEST CIRCUITS
THS4520
CM
From
50
Source
W
V
IN
0.22 Fm
49.9 W
R
F
R
IT
V
S+
V
S-
1:1
V
OUT
Open
To50 W
Test
Equipment
R
G
R
IT
R
F
R
O
R
OT
R
O
Frequency Response
THS4520
SLOS503B – SEPTEMBER 2006 – REVISED JULY 2007
CM SMALL SIGNAL FREQUENCY RESPONSE
Figure 54.
GAIN R
F
R
G
R
IT
20 dB 499 Ω 34.8 Ω 115 Ω
Note: The gain setting includes 50- Ω source
The THS4520 is tested with the following test circuits
impedance. Components are chosen to achieve gain
built on the EVM. For simplicity, power supply
and 50- Ω input termination.
decoupling is not shown – see layout in the
applications section for recommendations.
Table 2. Load Component Values
R
L
R
O
R
OT
Atten.
100 Ω 25 Ω open 6 dB
200 Ω 86.6 Ω 69.8 Ω 16.8 dB
499 Ω 237 Ω 56.2 Ω 25.5 dB
1 k Ω 487 Ω 52.3 Ω 31.8 dB
2 k 976 51.1 –37.86
Note: The total load includes 50- Ω termination by the
test equipment. Components are chosen to achieve
Figure 55. General Test Circuit for Device Testing
load and 50- Ω line termination through a 1:1
and Characterization
transformer.
Due to the voltage divider on the output formed by
Depending on the test conditions, component values
the load component values, the amplifier's output is
are changed per the following tables, or as otherwise
attenuated in test. The column Atten in Table 2
noted. The signal generators used are ac coupled
shows the attenuation expected from the resistor
50- Ω sources and a 0.22- μ F capacitor and a 49.9- Ω
divider. When using a transformer at the output the
resistor to ground are inserted across R
IT
on the
signal will have slightly more loss, and the numbers
alternate input to balance the circuit. A split power
will be approximate.
supply is used to ease the interface to common test
equipment, but the amplifier can be operated
single-supply as described in the applications section
with no impact on performance.
The general circit shown in Figure 55 is modified as
shown in Figure 56 , and is used to measure the
Table 1. Gain Component Values
frequency response of the device.
GAIN R
F
R
G
R
IT
A network analyzer is used as the signal source and
0 dB 499 Ω 487 Ω 53.6 Ω
as the measurement device. The output impedance
6 dB 499 Ω 243 Ω 57.6 Ω
10 dB 499 Ω 147 Ω 63.4 Ω
14 dB 499 Ω 88.7 Ω 71.5 Ω
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