THS4500-EP Datasheet, PDF (21/38 Pages) National Semiconductor (TI) – WIDEBAND, LOW-DISTORTION, FULLY DIFFERENTIAL AMPLIFIER

THS4500-EP
www.ti.com
SLOS832 – JUNE 2013
APPLICATION INFORMATION
FULLY DIFFERENTIAL AMPLIFIERS
FULLY DIFFERENTIAL AMPLIFIER
TERMINAL FUNCTIONS
Differential signaling offers a number of performance
advantages in high-speed analog signal processing
systems, including immunity to external common-
mode noise, suppression of even-order nonlinearities,
and increased dynamic range. Fully 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 designs using these
amplifiers.
Fully differential amplifiers are typically packaged in
eight-pin packages, as shown in Figure 98. The
device pins include two inputs (V_IN+, V_IN–), two
outputs (V_OUT–, V_OUT+), two power supplies (V_S+, V_S–),
an output common-mode control pin (V_OCM), and an
optional power-down pin (PD).
V_IN- 1
V_{OCM 2}
V_{S+ 3}
V_OUT+ 4
8 V_IN+
7 PD
6 V_S-
5 V_OUT-
Figure 98. Fully Differential Amplifier Pin Diagram
APPLICATIONS SECTION
• Fully Differential Amplifier Terminal Functions
• Input Common-Mode Voltage Range and the
THS4500 Family
• Choosing the Proper Value for the Feedback and
Gain Resistors
• Application Circuits Using Fully Differential
Amplifiers
• Key Design Considerations for Interfacing to an
Analog-to-Digital Converter
• Setting the Output Common-Mode Voltage With
the V_OCM Input
• Saving Power with Power-Down Functionality
• Linearity: Definitions, Terminology, Circuit
Techniques, and Design Tradeoffs
• An Abbreviated Analysis of Noise in Fully
Differential Amplifiers
• Printed-Circuit Board Layout Techniques for
Optimal Performance
• Power Dissipation and Thermal Considerations
• Power Supply Decoupling Techniques and
Recommendations
• Evaluation Fixtures, Spice Models, and
Applications Support
• Additional Reference Material
xxx
xxx
A standard configuration for the device is shown in
Figure 98. The functionality of a fully differential
amplifier can be imagined as two inverting amplifiers
that share a common noninverting terminal (though
the voltage is not necessarily fixed). For more
information on the basic theory of operation for fully
differential amplifiers, refer to the Texas Instruments
application note Fully Differential Amplifiers, literature
number SLOA054.
INPUT COMMON-MODE VOLTAGE RANGE
AND THE THS4500 FAMILY
The key difference between the THS4500/1 and the
THS4502/3 is the input common-mode range for the
four devices. The THS4502 and THS4503 have an
input common-mode range that is centered around
midrail, and the THS4500 and THS4501 have an
input common-mode range that is shifted to include
the negative power-supply rail. Selection of one or
the other amplifier is determined by the nature of the
application. Specifically, the THS4500 and THS4501
are designed for use in single-supply applications
where the input signal is ground-referenced, as
depicted in Figure 99. The THS4502 and THS4503
are designed for use in single-supply or split-supply
applications where the input signal is centered
between the power-supply voltages, as depicted in
Figure 100.
Copyright © 2013, Texas Instruments Incorporated
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