Tri path Technol og y, I nc. - Techni cal I nformation
Amplifier Gain
The gain of an amplifier based on the TCA2002 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 for the various
amplifier configurations.
A
VTK2150
=
A
VINPUTSTAG
E
* A
V MODULATOR
For example, using a TCA2002 with the following external components, in a Single Ended, Split
Supply Application
R
I
= 20kΩ
R
F
= 30.1kΩ
R
FBA
= 1kΩ
R
FBB
= 1.1kΩ
R
FBC
= 10.0kΩ
A
VTCA2002
≈ −
20k
Ω
10.0k
Ω
* (1.0k
Ω
+
1.1k
Ω
)
V
+
1
=
- 13.35
30.1k
Ω
1.0k
Ω
* 1.1k
Ω
V
Input Stage Design
The TCA2002 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.
TCA2002
OAOUT1
RF
RI
INV1
V5
CI
INPUT1
-
+
BIASCAP
AGND
V5
+
INV2
-
CI
INPUT2
RF
RI
OAOUT2
AGND
Figure 2: Input Stage
The gain of the input stage, above the low frequency high pass filter point, is that of a simple inverting
amplifier: It should be noted that the input amplifiers are biased at approximately 2.5VDC. Thus, the
polarity of C
I
must be followed as shown in Figure 2 for a standard ground referenced input signal
A
V
INPUT STAGE
=−
R
F
R
I
9
TCA2002 – KLi/0.95/04.06
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
