Tripath Technology, Inc. - Technical Information
loads and the impedance they present changes over frequency and from speaker model to
speaker model.
Tripath recommends designing the filter as a 2nd order, 100kHz LC filter. Tripath has obtained
good results with LF = 18uH and CF = 0.15uF.
The core material of the output filter inductor has an effect on the distortion levels produced by a
TK2150 amplifier. Tripath recommends low-mu type-2 iron powder cores because of their low
loss and high linearity (available from Micrometals, www.micrometals.com). The specific core
used on the EB-TK2150 was a T106-2 wound with 44 turns of 22AWG wire.
Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load
operation of a TK2150 amplifier can create significant peaking in the LC filter, which produces
strong resonant currents that can overheat the output MOSFETs and/or other components. The
RC dampens the peaking and prevents problems. Tripath has obtained good results with RZ =
20Ω and CZ = 0.15uF.
Bridging the TK2150
The TK2150 can be bridged by returning the signal from VP1 to the input resistor at INV2. OUT1
will then be a gained version of VP1, and OUT2 will be a gained and inverted version of OAOUT1
(see Figure 8). When the two amplifier outputs are bridged, the apparent load impedance seen
by each output is halved, so the current capability of the output MOSFETs, as well their power
dissipation capability, must be accounted for in the design. In addition, the higher peak currents
caused by driving lower impedance loads will cause additional ringing on the outputs. Thus, the
layout and supply decoupling for low impedance (below 8 ohms) bridged applications must be
extremely good to minimize output ringing and to ensure proper amplifier performance.
TC2001
OAOUT1
22
V5
CI
RI
RF
INV1 23
+
-
+
INPUT1
AGND
BIASCAP
V5
20k
20k
+
-
INV2 28
AGND
OAOUT2
27
Figure 8: Input Stage Setup for Bridging
28
TK2150 – Rev. 1.0/12.02
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