THS4502SLASH3 datasheet(21/40 Pages) TI1

21 / 40 page

THS4503−EP

SGLS291A − APRIL 2005 − JANUARY 2012

www.ti.com

FULLY DIFFERENTIAL AMPLIFIER

TERMINAL FUNCTIONS

Fully differential amplifiers are typically packaged in 8-pin

packages as shown in the diagram. The device pins

include two inputs (VIN+, VIN−), two outputs (VOUT−,

VOUT+), two power supplies (VS+, VS−), an output

common-mode control pin (VOCM), and an optional

power-down pin (PD).

VIN− 1

VOCM

VS+

VOUT+

VIN+

VS−

VOUT−

Fully Differential Amplifier Pin Diagram

A standard configuration for the device is shown in the

figure. 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, see the

Texas Instruments application note titled Fully Differential

Amplifiers (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 two

devices. The THS4503 has 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 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 94. The THS4503 is 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 95.

Figure 94

VOCM

+VS

Rg1

Rg2

Rf1

Rf2

−

Application Circuit for the THS4500 and THS4501,

Featuring Single-Supply Operation With a

Ground-Referenced Input Signal

Figure 95

VOCM

+VS

Rg1

Rg2

Rf1

Rf2

−

−VS

Application Circuit for the THS4500 and THS4501,

Featuring Split-Supply Operation With an Input

Signal Referenced at the Midrail

Equations 1−5 allow for calculation of the required input

common-mode range for a given set of input conditions.

The equations allow calculation of the input common-

mode range requirements given information about the

input signal, the output voltage swing, the gain, and the

output common-mode voltage. Calculating the maximum

and minimum voltage required for VN and VP (the

amplifier’s input nodes) determines whether or not the

input common-mode range is violated or not. Four

equations are required. Two calculate the output voltages

and two calculate the node voltages at VN and VP (note

that only one of these needs calculation, as the amplifier

forces a virtual short between the two nodes).

THS4502/3 Datasheet(PDF) 21 Page - Texas Instruments

THS4502/3 Datasheet(HTML) 21 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Datasheet Download

Link URL