THS4522IPW datasheet(24/71 Pages) TI2

24 / 71 page

THS4521, THS4522, THS4524

SBOS458H – DECEMBER 2008 – REVISED JUNE 2015

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8 Detailed Description

8.1 Overview

The THS4521, THS4522, and THS4524 family is tested with the test circuits shown in this section; all circuits are

built using the available THS4521 evaluation module (EVM). For simplicity, power-supply decoupling is not

shown; see the layout in the Typical Applications section for recommendations. Depending on the test conditions,

component values change in accordance with Table 4 and Table 5, or as otherwise noted. In some cases the

signal generators used are ac-coupled and in others they dc-coupled 50-

Ω sources. To balance the amplifier

when ac-coupled, a 0.22-

μF capacitor and 49.9-Ω resistor to ground are inserted across RIT on the alternate

input; when dc-coupled, only the 49.9-

Ω resistor to ground is added across RIT. A split power supply is used to

ease the interface to common test equipment, but the amplifier can be operated in a single-supply configuration

as described in the Typical Applications section with no impact on performance. Also, for most of the tests,

except as noted, the devices are tested with single-ended inputs and a transformer on the output to convert the

differential output to single-ended because common lab test equipment has single-ended inputs and outputs.

Similar or better performance can be expected with differential inputs and outputs.

As a result of the voltage divider on the output formed by the load component values, the amplifier output is

attenuated. The Atten column in Table 5 shows the attenuation expected from the resistor divider. When using a

transformer at the output (as shown in Figure 55), the signal sees slightly more loss because of transformer and

line loss; these numbers are approximate.

Table 4. Gain Component Values for Single-Ended Input (see Figure 54)

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

191

Ω

59.0

Ω

10 V/V

1 k

Ω

86.6

Ω

69.8

Ω

1. Gain setting includes 50-

Ω source impedance. Components are chosen to achieve gain and 50-Ω input

termination.

Table 5. Load Component Values For 1:1 Differential To Single-Ended Output Transformer (See

Figure 55)

ROT

Atten

100

Ω

24.9

Ω

Open

6 dB

200

Ω

86.6

Ω

69.8

Ω

16.8 dB

499

Ω

237

Ω

56.2

Ω

25.5 dB

1 k

Ω

487

Ω

52.3

Ω

31.8 dB

1. Total load includes 50-

Ω termination by the test equipment. Components are chosen to achieve load and 50-

Ω line termination through a 1:1 transformer.

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