Tripath Technology, Inc. - Technical Information
The TC2001 incorporates a differential feedback system to minimize the effects of ground bounce
and cancel out common mode ground noise. As such, the feedback from the output ground for
each channel needs to be properly sensed. This can be accomplished by connecting the output
ground “sensing” trace directly to the star formed by the output ground return, output capacitor,
CO, and the zobel capacitor, CZ. Refer to the Application / Test Circuit for a schematic
description.
TK2150 Amplifier Gain
The gain of the TK2150 is the product of the input stage gain and the modulator gain for the
TC2001. Please refer to the sections, Input Stage Design, and Modulator Feedback Design, for a
complete explanation of how to determine the external component values.
A
A
VTK2150 = AVINPUTSTAG
E
* AV MODULATOR
R
F
R
FBC * (RFBA + RFBB )
VTK2150 ≈ −
+ 1
R
I
R
FBA * RFBB
For example, using a TC2001 with the following external components,
RI = 20kΩ
RF = 30.1kΩ
R
FBA = 1kΩ
RFBB = 1.1kΩ
RFBC = 10.0kΩ
20k Ω 10.0k Ω * (1.0k Ω + 1.1k Ω)
V
V
A
VTK2150 ≈ −
+ 1 = -13.35
30.1k Ω
1.0k Ω * 1.1k Ω
Input Stage Design
The TC2001 input stage is configured as an inverting amplifier, allowing the system designer
flexibility in setting the input stage gain and frequency response. Figure 2 shows a typical
application where the input stage is a constant gain inverting amplifier. The input stage gain
should be set so that the maximum input signal level will drive the input stage output to 4Vpp.
The gain of the input stage, above the low frequency high pass filter point, is that of a simple
inverting amplifier:
R
R
F
A
VINPUTSTAG E = −
I
18
TK2150 – Rev. 1.0/12.02
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