THS4521 datasheet(22/48 Pages) TI

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THS452x

24.9 W

953 W

1kW

49.9 W

24.9 W

OCM

IN+

Measurewith

Differential

Probe

AcrossR

Installedto

Balance

Amplifier

Calibrated

Differential

Probe

Across

Open

From

50-

Source

S+

S-

0.22 F

THS4521

THS4522

THS4524

SBOS458D – DECEMBER 2008 – REVISED AUGUST 2010

www.ti.com

TEST CIRCUITS

Table 2. Load Component Values For 1:1

Overview

Differential to Single-Ended Output Transformer(1)

The THS4521, THS4522, and THS4524 family is

ROT

Atten

tested with the test circuits shown in this section; all

100

Ω

24.9

Ω

Open

6 dB

circuits

are

built

using

the

available

THS4521

200

Ω

86.6

Ω

69.8

Ω

16.8 dB

evaluation

module

(EVM).

For

simplicity,

power-supply decoupling is not shown; see the layout

499

Ω

237

Ω

56.2

Ω

25.5 dB

in the Applications section for recommendations.

1 k

Ω

487

Ω

52.3

Ω

31.8 dB

Depending on the test conditions, component values

1. Total load includes 50-

Ω termination by the test

change in accordance with Table 1 and Table 2, or

equipment. Components are chosen to achieve

as otherwise noted. In some cases the signal

load and 50-

Ω line termination through a 1:1

generators used are ac-coupled and in others they

transformer.

dc-coupled 50-

Ω sources. To balance the amplifier

when ac-coupled, a 0.22-mF capacitor and 49.9-Ω

Frequency Response

resistor to ground are inserted across RIT on the

alternate input; when dc-coupled, only the 49.9-

Ω

The circuit shown in Figure 53 is used to measure the

resistor to ground is added across RIT. A split power

frequency response of the circuit.

supply is used to ease the interface to common test

An HP network analyzer is used as the signal source

equipment, but the amplifier can be operated in a

and the measurement device. The output impedance

single-supply

configuration

described

the

of the HP network analyzer is is dc-coupled and is

Applications section with no impact on performance.

Ω. RIT and RG are chosen to impedance-match to

Also, for most of the tests, except as noted, the

Ω and maintain the proper gain. To balance the

devices are tested with single-ended inputs and a

amplifier, a 49.9-

Ω resistor to ground is inserted

transformer on the output to convert the differential

across RIT on the alternate input.

output to single-ended because common lab test

equipment has single-ended inputs and outputs.

The

output

probed

using

Tektronix

Similar or better performance can be expected with

high-impedance differential probe across the 953-

Ω

differential inputs and outputs.

resistor and referred to the amplifier output by adding

back the 0.42-dB because of the voltage divider on

As a result of the voltage divider on the output formed

the output.

by the load component values, the amplifier output is

attenuated. The Atten column in Table 2 shows the

attenuation expected from the resistor divider. When

using a transformer at the output (as shown in

Figure 54), the signal sees slightly more loss because

of transformer and line loss; these numbers are

approximate.

Table 1. Gain Component Values for

Single-Ended Input(1)

Gain

RIT

1 V/V

1 k

Ω

1 k

Ω

52.3

Ω

2 V/V

1 k

Ω

487

Ω

53.6

Ω

5 V/V

1 k

Ω

187

Ω

59.0

Ω

10 V/V

1 k

Ω

86.6

Ω

69.8

Ω

Figure 53. Frequency Response Test Circuit

1. Gain setting includes 50-

Ω source impedance.

Components are chosen to achieve gain and

50-

Ω input termination.

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