THS4501CDG4 datasheet(22/48 Pages) TI1

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OCM

S+

OUT+

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OUT

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 (VIN+, VIN–), two

systems,

including

immunity

external

outputs (VOUT–, VOUT+), two power supplies (VS+, VS–),

common-mode noise, suppression of even-order

an output common-mode control pin (VOCM), 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 VOCM 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

•

Abbreviated

Analysis

Noise

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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