LA42101
No.A0740-4/7
External Components
C1
: The input coupling capacitors, for which 4.7
μF or less is recommended. LA42101 employs the zero-bias type
input circuit, with the input pin potential being nearly zero (about 0.01V). Accordingly, the polarity must be
determined according to the DC potential of a circuit connected to the previous stage of LA42101.
C2
: Capacitor for starting time of the ripple filter and amplifier, for which 47
μF is recommended.
C3, R1
: Capacitor and resistor for mute. C3 is necessary even when the mute function is not used.
C4
: Power capacitor.
C5, C6
: Capacitor and resistor for oscillation prevention. For C5, C6, the polyester film capacitor with superior
R2, R3
temperature characteristics (Mylar capacitor) is recommended. Use R2, R3 of 2.2
Ω along with the capacitor.
1. Mute function (pin 6)
With the pin 6 voltage of 1.5V (minimum) or more, the mute function is turned ON.
Set the VM application voltage so that the pin 6 voltage becomes. 1.5V or more.
The mute time constant is determined by R1 and C3. Determine the constant after careful review because it is related
to the pop sound at mute ON/OFF.
C4 is necessary even when the mute function is not used because it is related to the pop sound when the amplifier is
turned ON.
Example : The pin 6 voltage becomes about 1.8V when VM = 5V and R1 = 15kΩ.
Note that the MUTE pin (pin 6) incorporates the anti-static
diodo and that decrease of the VCC pin 7 potential below that of
pin 6 causes the current to flow through the diode.
2. Standby function (pin 5)
The amplifier is turned ON when the voltage of 2.5V (minimum) or more is applied to pin 5.
Pin 5 control voltage
Pin 5 voltage
Amplifier
Standby
0 to 0.5
OFF
ON
2.5 to VCC
ON
OFF
To suppress the inrush current to pin 5 when the VSTB
application voltage is high, insert the control resistor (RSTB).
Example : Tosuppress the pin 5 inrush current to 500
μA or less
RSTB =
Applied voltage (VSTB) -2VBE (About 1.4V)
500
μA
-15k
Ω
Note that the standby pin (pin 5) incorporates the anti-electrostatic diode, allowing the cu orrent to flow through the
diode when the potential of VCC pin 7 decreases below that of pin 5.
Mute
Standby
+
6
C3
10
μF
R1
2k
Ω
2k
Ω
VCC
VM
20k
Ω
5
RSTB
1.5k
Ω
15k
Ω
VCC
2VBE
VS
30k
Ω