TPA301
350-mW MONO AUDIO POWER AMPLIFIER
SLOS208C – JANUARY1998 – REVISED MARCH 2000
APPLICATION INFORMATION
application schematic
Figure 26 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of
–10 V/V.
V
6
5
DD
R
50 kΩ
C
5 pF
F
F
V
DD
C
S
V
DD
/2
Audio
Input
1 µF
IN –
IN+
4
V
O
+
–
+
C
R
I
3
I
0.47 µF 10 kΩ
2
BYPASS
C
B
2.2 µF
–
+
350 mW
V
O
–
8
7
GND
SHUTDOWN
1
Bias
Control
From System Control
Figure 26. TPA301 Application Circuit
The following sections discuss the selection of the components used in Figure 26.
component selection
gain setting resistors, R and R
F
I
The gain for each audio input of the TPA301 is set by resistors R and R according to equation 5 for BTL mode.
F
I
R
F
BTL Gain
A
2
(5)
V
R
I
BTL mode operation brings about the factor 2 in the gain equation due to the inverting amplifier mirroring the
voltage swing across the load. Given that the TPA301 is a MOS amplifier, the input impedance is very high,
consequently input leakage currents are not generally a concern although noise in the circuit increases as the
value of R increases. In addition, a certain range of R values are required for proper start-up operation of the
F
F
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 6.
R R
F I
Effective Impedance
(6)
R
R
F
I
15
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