Tripath Technology, Inc. - Technical Information
spectrum and typically varies between 200kHz and 1.5MHz, which is well above the 20Hz –
22kHz audio band. The pattern itself does not alter or distort the audio input signal but it does
introduce some inaudible noise components.
The measurements of certain performance parameters, particularly those that have anything to
do with noise, like THD+N, are significantly affected by the design of the low-pass filter used on
the output of the TK2150 and also the bandwidth setting of the measurement instrument used.
Unless the filter has a very sharp roll-off just past the audio band or the bandwidth of the
measurement instrument ends there, some of the inaudible noise components introduced by the
Tripath amplifier switching pattern will get integrated into the measurement, degrading it.
Tripath amplifiers do not require large multi-pole filters to achieve excellent performance in
listening tests, usually a more critical factor than performance measurements. Though using a
multi-pole filter may remove high-frequency noise and improve THD+N type measurements
(when they are made with wide-bandwidth measuring equipment), these same filters can
increase distortion due to inductor non-linearity. Multi-pole filters require relatively large
inductors, and inductor non-linearity increases with inductor value.
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TK2150 – Rev. 1.0/12.02
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
