Datasheet

THS770006
SBOS520B –JULY 2010–REVISED JANUARY 2012 www.ti.com
TEST CIRCUITS
OVERVIEW
The standard THS770006 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 33. The signal
generators and analyzers used for most tests have single-ended 50Ω input and output impedance. The
THS770006 EVM is configured to convert to and from a differential 50Ω impedance by using RF transformers or
baluns (CX2156NL from Pulse, supplied as a standard configuration of the EVM). 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.
A resistor network is used on the amplifier output to present various loads (R
L
) 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
L
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.
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