EXAMPLE ANALOG-TO-DIGITAL

V

OCM

15V

V

S

R

S

R

G

R

F

R

F

+

R

T

+

R

G

C

G

0.1 mF

C

G

THS4504

V

DD

C

S

C

S

R

L

V

OD

PP

=26V

R

ISO

R

ISO

-

-

FILTERING WITH FULLY DIFFERENTIAL

+

+

VOCM

12-Bit/80MSPS

IN

IN

5 V

CM

5 V

5 V

VS

10 mF

0.1 mF

10 mF 0.1 mF

THS4503

RF

RF

CF

CF

1 mF

RG

RG

0.1 mF

RT

RS

ADS5410

RISO

RISO

-

-

+

+

V

OCM

14-Bit/40MSPS

IN

IN

5 V

CM

5 V

V

S

10 mF

0.1 mF

THS4501

R

F

R

F

C

F

C

F

1 mF

R

G

R

G

R

T

R

S

ADS5421

0.1

F

m

R

ISO

R

ISO

-

-

VS

RS

RG1

RF1

RF2

+

RT

+

VO

RISO

C

CF2

CF1

RG2

RISO

-

-

FULLY DIFFERENTIAL LINE DRIVERS

THS4504

THS4505

www.ti.com ......................................................................................................................................................... SLOS363D – AUGUST 2002 – REVISED MAY 2008

Figure 81 illustrates the THS4500 family of devices

CONVERTER DRIVER CIRCUITS

used as high speed line drivers. For line driver

applications, close attention must be paid to thermal

The THS4500 family of devices is designed to drive

design constraints due to the typically high level of

high-performance ADCs with extremely high linearity,

power dissipation.

allowing for the maximum effective number of bits at

the output of the data converter. Two representative

circuits shown below highlight single-supply operation

and split supply operation. Specific feedback resistor,

gain resistor, and feedback capacitor values are not

specified, as their values depend on the frequency of

interest. Information on calculating these values can

be found in the applications material above.

Figure 81. Fully Differential Line Driver with High

Output Swing

AMPLIFIERS

Similar

to

their

single-ended

counterparts,

fully

differential amplifiers have the ability to couple

filtering functionality with voltage gain. Numerous filter

topologies

can

be

based

on

fully

differential

amplifiers. Several of these are outlined in A

Figure 79. Using the THS4503 with the ADS5410

Differential Circuit Collection (SLOA064), referenced

at the end of this data sheet. The circuit in Figure 82

depicts a simple two-pole low-pass filter applicable to

many different types of systems. The first pole is set

by the resistors and capacitors in the feedback paths,

and the second pole is set by the isolation resistors

and the capacitor across the outputs of the isolation

resistors.

Figure 80. Using the THS4501 with the ADS5421

Figure 82. A Two-Pole, Low-Pass Filter Design

The THS4500 family of amplifiers can be used as

Using a Fully Differential Amplifier with Poles

high-frequency, high-swing differential line drivers.

Located at P1 = (2

×R

FCF)

–1 in Hz and

Their high power supply voltage rating (16.5 V

P2 = (4

×R

ISOC)

–1 in Hz

absolute maximum) allows operation on a single 12-V

or a single 15-V supply. The high supply voltage,

coupled with the ability to provide differential outputs

enables the ability to drive 26 VPP into reasonably

heavy loads (250

Ω or greater). The circuit in

Copyright © 2002–2008, Texas Instruments Incorporated

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