VGEN
CIN
CL
RIN
RGEN
Twisted-PairWire
Generator
EvaluationModule
AudioPower
Amplifier
Twisted-PairWire
RL
RANA
CANA
Analyzer
RANA
CANA
Lfilt
Cfilt
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SLOS541C – JULY 2007 – REVISED AUGUST 2010
SE Input and SE Output (TPA3123D2 Stereo Configuration)
The SE input and output configuration is used with class-AB amplifiers. A block diagram of a fully SE
measurement circuit is shown in
Figure 30. SE inputs normally have one input pin per channel. In some cases,
two pins are present; one is the signal and the other is ground. SE outputs have one pin driving a load through
an output ac-coupling capacitor and the other end of the load is tied to ground. SE inputs and outputs are
considered to be unbalanced, meaning one end is tied to ground and the other to an amplifier input/output.
The generator should have unbalanced outputs, and the signal should be referenced to the generator ground for
best results. Unbalanced or balanced outputs can be used when floating, but they may create a ground loop that
affects the measurement accuracy. The analyzer should have balanced inputs to cancel out any common-mode
noise in the measurement.
Figure 30. SE Input—SE Output Measurement Circuit
The following general rules should be followed when connecting to APAs with SE inputs and outputs:
Use an unbalanced source to supply the input signal.
Use an analyzer with balanced inputs.
Use twisted-pair wire for all connections.
Use shielding when the system environment is noisy.
Ensure the cables from the power supply to the APA, and from the APA to the load, can handle the large
Copyright 2007–2010, Texas Instruments Incorporated
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