Datasheet

V
IN-
1
2
3
4
8
7
6
5
V
OCM
V
S+
V
OUT+
V
IN+
V
S-
V
OUT-
PD
THS4500
THS4501
SLOS350F –APRIL 2002–REVISED OCTOBER 2011 www.ti.com
APPLICATION INFORMATION
FULLY DIFFERENTIAL AMPLIFIER
TERMINAL FUNCTIONS
FULLY DIFFERENTIAL AMPLIFIERS
Fully differential amplifiers are typically packaged in
Differential signaling offers a number of performance
eight-pin packages, as shown in Figure 97. The
advantages in high-speed analog signal processing
device pins include two inputs (V
IN+
, V
IN–
), two
systems, including immunity to external
outputs (V
OUT–
, V
OUT+
), two power supplies (V
S+
, V
S–
),
common-mode noise, suppression of even-order
an output common-mode control pin (V
OCM
), and an
nonlinearities, and increased dynamic range. Fully
optional power-down pin (PD).
differential amplifiers not only serve as the primary
means of providing gain to a differential signal chain,
but also provide a monolithic solution for converting
single-ended signals into differential signals for
easier, higher performance processing. The THS4500
family of amplifiers contains products in Texas
Instruments' expanding line of high-performance, fully
differential amplifiers. Information on fully differential
amplifier fundamentals, as well as implementation
specific information, is presented in the Applications
Section of this data sheet to provide a better
understanding of the operation of the THS4500 family
of devices, and to simplify the design process for
Figure 97. Fully Differential Amplifier Pin Diagram
designs using these amplifiers.
A standard configuration for the device is shown in
APPLICATIONS SECTION
Figure 97. The functionality of a fully differential
• Fully Differential Amplifier Terminal Functions
amplifier can be imagined as two inverting amplifiers
• Input Common-Mode Voltage Range and the
that share a common noninverting terminal (though
THS4500 Family
the voltage is not necessarily fixed). For more
information on the basic theory of operation for fully
• Choosing the Proper Value for the Feedback and
differential amplifiers, refer to the Texas Instruments
Gain Resistors
application note Fully Differential Amplifiers, literature
• Application Circuits Using Fully Differential
number SLOA054 , available for download
Amplifiers
at www.ti.com.
• Key Design Considerations for Interfacing to an
Analog-to-Digital Converter
INPUT COMMON-MODE VOLTAGE RANGE
• Setting the Output Common-Mode Voltage With
AND THE THS4500 FAMILY
the V
OCM
Input
The key difference between the THS4500/1 and the
• Saving Power with Power-Down Functionality
THS4502/3 is the input common-mode range for the
• Linearity: Definitions, Terminology, Circuit
four devices. The THS4502 and THS4503 have an
Techniques, and Design Tradeoffs
input common-mode range that is centered around
• An Abbreviated Analysis of Noise in Fully
midrail, and the THS4500 and THS4501 have an
Differential Amplifiers
input common-mode range that is shifted to include
• Printed-Circuit Board Layout Techniques for
the negative power-supply rail. Selection of one or
Optimal Performance
the other amplifier is determined by the nature of the
application. Specifically, the THS4500 and THS4501
• Power Dissipation and Thermal Considerations
are designed for use in single-supply applications
• Power Supply Decoupling Techniques and
where the input signal is ground-referenced, as
Recommendations
depicted in Figure 98. The THS4502 and THS4503
• Evaluation Fixtures, Spice Models, and
are designed for use in single-supply or split-supply
Applications Support
applications where the input signal is centered
• Additional Reference Material
between the power-supply voltages, as depicted in
Figure 99.
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Product Folder Link(s): THS4500 THS4501