THS4271D datasheet(28/38 Pages) TI

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THS4271

THS4275

SLOS397E − JULY 2002 − REVISED JANUARY 2004

www.ti.com

DESIGN TOOLS

Performance vs Package Options

The THS4271 and THS4275 are offered in different

package options. However, performance may be limited

due to package parasitics and lead inductance in some

packages. In order to achieve maximum performance of

the

THS4271

and

THS4275,

Texas

Instruments

recommends using the leadless MSOP (DRB) or MSOP

(DGN) packages, in addition to proper high-speed PCB

layout. Figure 92 shows the unity gain frequency response

of the THS4271 using the leadless MSOP, MSOP, and

SOIC package for comparison. Using the THS4271 and

THS4275 in a unity gain with the SOIC package may result

in the device becoming unstable. In higher gain

configurations, this effect is mitigated by the reduced

bandwidth. As such, the SOIC is suitable for application

with gains equal to or higher than +2 V/V or (−1 V/V).

Figure 92. Effects of Unity Gain Frequency

Response for Differential Packages

−4

−2

10 M

100 M

1 G

f − Frequency − Hz

49.9

Ω

150

Ω

SOIC, Rf = 0 Ω

SOIC,

Rf = 100 Ω

SOIC, Rf = 200 Ω

Leadless MSOP, &

MSOP Rf = 0 Ω

VIN = 100 mVPP

VS =±5 V

Evaluation Fixtures, Spice Models, and

Applications Support

Texas Instruments is committed to providing its customers

with the highest quality of applications support. To support

this goal, evaluation boards have been developed for the

THS4271 operational amplifier. Three evaluation boards

are available: one THS4271 and one THS4275, both are

configurable for different gains, and a third for a gain of +1

(THS4271 only). These boards are easy to use, allowing

for straightforward evaluation of the device. These

evaluation boards can be ordered through the Texas

Instruments web site, www.ti.com, or through your local

Texas Instruments sales representative. Schematics for

the evaluation boards are shown below.

The THS4271/THS4275 EVM board shown in Figure 96

through Figure 99 is designed to accommodate different

gain configurations. Its default component values are set

to give a gain of 2. The EVM can be configured in a gain

of +1; however, it is strongly not recommended. Evaluating

the THS4271/THS4275 in a gain of 1 using this EVM may

cause the part to become unstable. The stability of the

device can be controlled by adding a large resistor in the

feedback path, the performance is sacrificed. Figure 93

shows the small signal frequency response of the

THS4271 with different feedback resistors in the feedback

path. Figure 94 is the small frequency response of the

THS4271 using the gain of 1 EVM.

Figure 93. Frequency Response vs Feedback

Resistor Using the EDGE #6439527 EVM

−5

−3

−1

10M

100M

f − Frequency − Hz

49.9

Ω

150

Ω

VIN = 100 mVPP

VS = ±5 V

Rf = 150 Ω

Rf = 100 Ω

Rf = 50 Ω

Rf = 0 Ω

Figure 94. Frequency Response Using the

EDGE # 6443547 G = +1 EVM

−4

−3

−2

−1

100 k

1 M

10 M

100 M

1 G

10 G

f − Frequency − Hz

Gain = 1

RL = 150 Ω

VO = 100 mVPP

VS = ±5 V

49.9

Ω

150

Ω

The peaking in the frequency response is due to the lead

inductance in the feedback path. Each pad and trace on a

PCB has an inductance associated with it, which in

conjunction with the inductance associated with the

package may cause peaking in the frequency response,

causing the device to become unstable.

THS4271D Datasheet(PDF) 28 Page - Texas Instruments

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