Datasheet

THS770012

SLOS669C –FEBRUARY 2010–REVISED JANUARY 2012

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TEST CIRCUITS

OVERVIEW

The standard THS770012 evaluation module (EVM) is used for testing the typical performance shown in the

Typical Characteristics, with changes as noted below. The EVM schematic is shown in Figure 37. The signal

generators and analyzers used for most tests have single-ended 50Ω input and output impedance. The

THS770012 EVM is configured to convert to and from a single-ended 50Ω impedance by using RF transformers

or baluns 1:1 (CX2156NL from Pulse, supplied as a standard configuration of the EVM) to allow easy connection

to standard lab equipment. For line input termination, two 49.9Ω resistors (R5 and R6) are placed to ground on

the input transformer output pins (terminals 1 and 3). In combination with the 100Ω input impedance of the

device, the total impedance seen by the line is 50Ω.

Gain is set by placing external components R11, R12, R13, and R14 as described below in Setting the Gain

section.

A resistor network is used on the amplifier output to present various loads (R

) and maintain line output

termination to 50Ω. Depending on the test conditions, component values are changed as shown in Table 1, or as

otherwise noted. As a result of the voltage divider on the output formed by the load component values, the

amplifier output is attenuated. The Loss column in Table 1 shows the attenuation expected from the resistor

divider. The output transformer causes slightly more loss, so these numbers are approximate.

Table 1. Load Component Values

(1)

LOAD R

R15 AND R17 R16 LOSS

100Ω 25Ω Open 6dB

200Ω 86.6Ω 69.8Ω 16.8dB

400Ω 187Ω 57.6Ω 25.5dB

1kΩ 487Ω 52.3Ω 31.8dB

(1) The total load includes 50Ω termination by the test equipment. Components are chosen to achieve load and 50Ω line termination

through a 1:1 transformer.

Product Folder Link(s): THS770012