apa2071 Anpec Electronics Corporation, apa2071 Datasheet - Page 17

• Manufacturer Part Number: apa2071
• Description: Stereo 3.1w Non-inverting Audio Power Amplifier With Dc Volume Control
• Manufacturer: Anpec Electronics Corporation

Application Information
APA2071
Input Capacitor (C
In the typical application, an input capacitor, C
to allow the amplifier to bias the input signal to the proper
DC level for optimum operation. In this case, C
fixed input impedance R
corner frequency is determined in the following equation:
The value of C
directly affects the low frequency performance of the
circuit. Consider the example where R
specification calls for a flat bass response down to 40Hz.
The equation is reconfigured below :
Consider the variation of input resistance (R
of C
value in the range from 0.22 F to 1.0 F. A further consid-
eration for this capacitor is the leakage path from the in-
put source through the input network (R
load.
This leakage current creates a DC offset voltage at the
input to the amplifier that reduces useful headroom, es-
pecially in high gain applications. For this reason, a low-
leakage tantalum or ceramic capacitor is the best choice.
When polarized capacitors are used, the positive side of
the capacitors should face the amplifiers’ inputs in most
applications because the DC level of the amplifiers’ in-
puts are held at V
confirm the capacitor polarity in the application.
Effective Bypass Capacitor (C
A power amplifier, proper supply bypassing, is critical for
low noise performance and high power supply rejection.
The capacitor location on the BYPASS pin should be as
close to the device as possible. The effect of a larger
supply bypass capacitor is to improve PSRR due to in-
creased half-supply stability. Two critical criteria of by-
pass capacitor (C
requirements and click-and-pop performance; 2
leakage current of C
V
Copyright
Rev. A.1 - Aug., 2008
BYPASS
i
f
C
should be 0.2 F. Therefore, it’ s better to choose a
C(highpass
i
(voltage of BYPASS pin), and if the V
2
R
1
)
ANPEC Electronics Corp.
i
f
i
c
must be considered carefully because it
BYPASS
2
DD
i
)
R
1
/2. Please note that it is important to
BYPASS
i
C
): 1
i
st
i
form a high-pass filter with the
, it depends upon desired PSRR
will induce the voltage drop of
BYPASS
)
i
is 20k
i
+ R
BYPASS
i
i
), the value
, is required
f
, C
i
and the
and the
i
) to the
is less
nd
(2)
(3)
, the
17
than 0.485V
value of V
Where
I
Therefore, it is recommended that C
rent should be no more than 0.5 A for properly work of
the APA2071.
The capacitor is fed from a 130k
the amplifier and the 20k is the fixed input resistance.
Bypass capacitor, C
ramic or tantalum low-ESR capacitors are recom-
mended for the best THD+N and noise performance.
The bypass capacitance also affects the start-up time. It
is determined in the following equation:
Output Coupling Capacitor (C
In the typical single-supply SE configuration, an output
coupling capacitor (C
the output of the amplifier thus preventing DC currents in
the load. As with the input coupling capacitor, the output
coupling capacitor and impedance of the load form a high-
pass filter governed by the equation.
For example, a 330 F capacitor with an 8 speaker would
attenuate low frequencies below 60.6Hz. The main
disadvantage, from a performance standpoint, is the load
To avoid start-up pop noise, the bypass voltage should
rise slower than the input bias voltage and the relation-
ship shown in equation should be maintained.
Leakage
T
F
V
(
C
start
BYPASS
C
=Leakage current of C
(
highpass
BYPASS
up
BYPASS
DD
5X(C
)
, the APA2071 will enter mute condition. The
1
0.5V
X130k
can be calculated as blew:
2
BYPASS
R
DD
1
L
C
C
I -
BYPASS
) is required to block the DC bias at
C
Leakage
)
X130k
, values of 2.2 F to 10 F ce-
BYPASS
C
C
i
130k
)
X20k
)
1
BYPASS
www.anpec.com.tw
resistor inside of
’ s leakage cur-
(
(
(
(
4)
7)
5)
6)