T E C H N I C A L I N F O R M A T I O N
A
A
VTA3020 = AVINPUTSTAG
E
* AV MODULATOR
R
F
R
FBC * (RFBA
R
FBB
)
+
+
VTA3020
1
≈ −
R
I
R
FBA * RFBB
For example, using a TA3020 with the following external components,
RI = 20kΩ
RF = 20kΩ
R
R
R
FBA = 1kΩ
FBB = 1.13kΩ
FBC = 9.09kΩ
20k Ω 13.3k Ω * (1.0k Ω 1.07k
)
V
V
+
Ω
A
VTA3020
1
-10.71
≈ −
+
=
49.9k Ω
1.0k Ω * 1.07k Ω
Input Stage Design
The TA3020 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.
TA3020
OAOUT1
V5
RF
CI
RI
-
+
INV1
INPUT1
BIASCAP
AGND
V5
+
-
INV2
RF
CI
RI
AGND
OAOUT2
INPUT2
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:
R
R
F
A
VINPUTSTAG E
= −
I
18
TA3020, Rev 2.1, 01.01
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
