LM4700 National Semiconductor, LM4700 Datasheet - Page 7

• Manufacturer Part Number: LM4700
• Description: Overture Audio Power Amplifier Series 30W Audio Power Amplifier with Mute and Standby Modes
• Manufacturer: National Semiconductor

10
11
12
13
14
15
16
17
Note 15: Optional components dependent upon specific design requirements.
External Components Description
1
2
3
4
5
6
7
8
9
Components
R
R
R
C
C
R
(Note 15)
R
(Note 15)
C
(Note 15)
R
(Note 15)
C
(Note 15)
L (Note 15)
R (Note 15)
R
C
R
(Note 15)
R
R
B
I
F
I
S
V
IN
IN
SN
SN
A
A
INP
BI
E
(Note 15)
Prevents currents from entering the amplifier’s non-inverting input which may be passed through to the
load upon power down of the system due to the low input impedance of the circuitry when the
undervoltage circuitry is off. This phenomenon occurs when the supply voltages are below 1.5V.
Inverting input resistance to provide AC gain in conjunction with R
at f
Feedback resistance to provide AC gain in conjunction with R
Feedback capacitor which ensures unity gain at DC.
Provides power supply filtering and bypassing. Refer to the Supply Bypassing application section for
proper placement and selection of bypass capacitors.
Acts as a volume control by setting the input voltage level.
Sets the amplifier’s input terminals DC bias point when C
to create a highpass filter at f
Input capacitor which blocks the input signal’s DC offsets from being passed onto the amplifier’s inputs.
Works with C
The pole is set at f
Works with R
Provides high impedance at high frequencies so that R may decouple a highly capacitive load and
reduce the Q of the series resonant circuit. Also provides a low impedance at low frequencies to short
out R and pass audio signals to the load. Refer to Figure 4 .
Provides DC voltage biasing for the transistor Q1 in single supply operation.
Provides bias filtering for single supply operation.
Limits the voltage difference between the amplifier’s inputs for single supply operation. Refer to the
Clicks and Pops application section for a more detailed explanation of the function of R
Provides input bias current for single supply operation. Refer to the Clicks and Pops application section
for a more detailed explanation of the function of R
Establishes a fixed DC current for the transistor Q1 in single supply operation. This resistor stabilizes the
half-supply point along with C
C
= 1/(2 R
SN
SN
I
C
I
to stabilize the output stage by creating a pole that reduces high frequency instabilities.
to stabilize the output stage by creating a pole that reduces high frequency instabilities.
).
C
= 1/(2 R
C
A
SN
.
= 1/(2 R
C
SN
). Refer to Figure 4 .
7
IN
Functonal Description
C
IN
). Refer to Figure 4 .
BI
.
IN
is present in the circuit. Also works with C
I
.
F
. Also creates a highpass filter with C
INP
.
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IN
I