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 50

Ω input and output impedance. The

THS770012 EVM is configured to convert to and from a single-ended 50

Ω 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 49.9

Ω resistors (R5 and R6) are placed to ground on

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

Ω input impedance of the

device, the total impedance seen by the line is 50

Ω.

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

section.

termination to 50

Ω. 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.

R15 AND R17

R16

LOSS

100

Ω

25

Ω

Open

6dB

200

Ω

86.6

Ω

69.8

Ω

16.8dB

400

Ω

187

Ω

57.6

Ω

25.5dB

1k

Ω

487

Ω

52.3

Ω

31.8dB

(1)

The total load includes 50

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

through a 1:1 transformer.

14

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