THS4531A_16 Datasheet, PDF (27/59 Pages) Texas Instruments – Ultra Low-Power, Rail-to-Rail Output, Fully Differential Amplifier

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9 Application and Implementation
THS4531A
SLOS823C – DECEMBER 2012 – REVISED JANUARY 2016
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
Figure 70 shows the general test circuit built on the EVM that was used for testing the THS4531A. For simplicity,
power supply decoupling is not shown – see Layout for recommendations. Depending on the test conditions,
component values are changed per Table 4 and Table 5, or as otherwise noted. Some of the signal generators
used are AC-coupled 50-Ω sources and a 0.22-µF capacitor and 49.9-Ω resistor to ground are inserted across
R_IT on the un-driven or alternate input as shown to balance the circuit. A split-power supply is used to ease the
interface to common lab test equipment, but if properly biased, the amplifier can be operated single-supply as
described in the applications section with no impact on performance. For most of the tests, the devices are
tested with single ended input and a transformer on the output to convert the differential output to single ended
because common lab test equipment have single ended inputs and outputs. Performance is the same or better
with differential input and differential output.
V_IN+
Input From 50-Ω
Test Equipment
R_G
PD
R_IT
0.22 µF
V_IN±
No Connection
0.22 µF
0.22 µF
R_G
R_IT
R_F
R_O
V_S+
V_OUT±
1:1
+
VOCM THS4531A
R_OT
±
V_S-
V_OUT+
R_O
R_F
Output to 50-Ω
Test Equipment
Installed to Balance
Amplifier's Feedback Networks
49.9 Ω
Figure 70. General Test Circuit
Table 4. Gain Component Values for Single-Ended Input⁽¹⁾
GAIN
1 V/V
2 V/V
5 V/V
10 V/V
R_F
2 kΩ
2 kΩ
2 kΩ
2 kΩ
R_G
2 kΩ
1 kΩ
392 Ω
187 Ω
R_IT
51.1 Ω
52.3 Ω
53.6 Ω
57.6 Ω
(1) Components are chosen to achieve gain and 50-Ω input termination. Resistor values shown are closest standard values so gains are
approximate.
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