Datasheet

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APPLICATION INFORMATION
SELECTION OF COMPONENTS
Audio
Input
Bias
Control
V
DD
= 5 V
6
1
5
7
V
O
1
V
O
2
V
DD
2
8
3
4
IN1
BYPASS
SHUTDOWN (see Note A)
V
DD
/2
C
I
R
I
R
F
C
F
50 kΩ 50 kΩ
C
B
C
S
NOTE A: SHUTDOWN must be held low for normal operation and asserted high for shutdown mode.
Audio
Input
C
I
R
I
IN2
R
F
C
F
R
L
R
L
C
C
C
C
Gain Setting Resistors, R
F
and R
I
Gain  

R
F
R
I

(1)
Effective Impedance 
R
F
R
I
R
F
 R
I
(2)
TPA302
SLOS174C – JANUARY 1997 – REVISED JUNE 2004
Figure 42 is a schematic diagram of a typical application circuit.
Figure 42. TPA302 Typical Notebook Computer Application Circuit
The gain for the TPA302 is set by resistors R
F
and R
I
according to Equation 1 .
Given that the TPA302 is an MOS amplifier, the input impedance is high; consequently, input leakage currents
are not generally a concern, although noise in the circuit increases as the value of R
F
increases. In addition, a
certain range of R
F
values is required for proper start-up operation of the amplifier. Taken together, it is
recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 kΩ and
20 kΩ. The effective impedance is calculated in Equation 2 .
As an example, consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The gain of the amplifier
would be –5 and the effective impedance at the inverting terminal would be 8.3 kΩ, which is within the
recommended range.
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