TA0105A Datasheet, PDF (16/29 Pages) Tripath Technology Inc. – STEREO CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DIGITAL POWER PROCESSING (DPPTM ) TECHNOLOGY

Tripath Technology, Inc. - Technical Information
TA0105A AMPLIFIER GAIN
The gain of the TA0105A is the product of the input stage gain and the modulator gain. 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 * A VTA0105A
VINPUTSTAG E
V MODULATOR
AVTA0105A ≈ − ^{20k Ω}  ^{(1.0k Ω + RFB) * 2.02} + 1
4.99k Ω + RI _
1020

For example, using a TA0105A with the following external components,
R_I = 34.8kΩ
R_FB = 39.2kΩ
AVTA0105A ≈ − ^{20k Ω}  ^{40.2k Ω * 2.02} + 1 = - 40.52 ^V
39.79k Ω _ 1020

V
INPUT STAGE DESIGN
The TA0105A input stage is an inverting amplifier, with a maximum gain of 4. 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. Please note that the
input is biased between V5 and AGND. Thus, the polarity of C_I must be observed.
The gain of the input stage, above the low frequency high pass filter point, is that of a simple inverting
amplifier:
A VINPUTSTAG E = −
20k Ω
4.99k Ω + RI
CI
INPUT1
TA0105A
V5
20K
RI
IN1 ^4.99K
CI
INPUT2
2.5V
AGND
V5
+
-
20K
RI
IN2 ^4.99K
AGND
Figure 2: Input Stage
16
TA0105A – RW/ Rev. 2.2/05.05