TA1101B Datasheet, PDF (11/13 Pages) Tripath Technology Inc. – Stereo 10W (4Ω) Class-T™ Digital Audio Amplifier using Digital Power Processing™ Technology

TECHNICAL INFORMATION
Performance Measurements of the TA1101B
The TA1101B operates by generating a high frequency switching signal based on the audio input. This
signal is sent through a low-pass filter (external to the Tripath amplifier) that recovers an amplified version
of the audio input. The frequency of the switching pattern is spread spectrum and typically varies between
100kHz and 1.0MHz, which is well above the 20Hz – 20kHz audio band. The pattern itself does not alter
or distort the audio input signal but it does introduce some inaudible components.
The measurements of certain performance parameters, particularly noise related specifications such as
THD+N, are significantly affected by the design of the low-pass filter used on the output as well as the
bandwidth setting of the measurement instrument used. Unless the filter has a very sharp roll-off just
beyond the audio band or the bandwidth of the measurement instrument is limited, some of the inaudible
noise components introduced by the Tripath amplifier switching pattern will degrade the measurement.
One feature of the TA1101B is that it does 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 degrade frequency
response. The TA1101B Evaluation Board uses the Test/Application Circuit in this data sheet, which has a
simple two-pole output filter and excellent performance in listening tests. Measurements in this data sheet
were taken using this same circuit with a limited bandwidth setting in the measurement instrument.
TA1101B, Rev. 2.2, 08.17.00
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