Tripath Technology, Inc. - Technical Information
For example, using a TK2050 with the following external components,
RI = 20kΩ
RF = 20kΩ
RFBB = 1kΩ
RFBC = 14kΩ
AVTK2050 ≈ 20k Ω 14k Ω + 1k Ω ) = 15 V
20k Ω 1k Ω V
Input Stage Design
The TC2000 input stage is configured as an inverting amplifier, allowing the system designer flexibility
in setting the input stage gain and frequency response. Figure 1 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.
INPUT1
RF
CI
RI
OAOUT1
INV1
TC2000
V5
-
+
BIASCAP
AGND
V5
INPUT2
RF
CI
RI
INV2
OAOUT2
+
-
AGND
Figure 1: 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 CI must be followed as shown in Figure 1 for a standard ground referenced input signal
A VINPUTSTAG E = − R F
RI
Input Capacitor Selection
CI can be calculated once a value for RI has been determined. CI and RI determine the input low
frequency pole. Typically this pole is set below 10Hz. CI is calculated according to:
CI= 1
2π fP R I
where:
RI = Input resistor value in ohms.
fP = Input low frequency pole (typically 10Hz or below)
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TK2050 – SB/1.0/8-02