la4815m Sanyo Semiconductor Corporation, la4815m Datasheet - Page 6

• Manufacturer Part Number: la4815m
• Description: Monaural Power Amplifier
• Manufacturer: Sanyo Semiconductor Corporation

Notes on Using the IC
1. Voltage gain settings (Pins 1 and 8)
2. Signal source impedance : rg
The voltage gain of the power amplifier is fixed by the internal resistors.
Note that the voltage gain can be changed using two resistors. (See Fig. 1)
In addition, the voltage gain can also be lowered to approximately 20dB (when using 5V or 6V power supply) by an
application such as shown in Fig. 2 below.
However, note that using this method to greatly lower the voltage gain deteriorates the characteristics, so the voltage
gain should be lowered only to approximately 20dB. In addition, when using a high supply voltage (7V or more), the
clipped waveform may invert, so this voltage gain reduction method must not be used in these cases.
The signal source impedance value rg affects the ripple rejection ratio together with input coupling capacitor Cin, so rg
should be as small as possible. Therefore, when attenuating the signal at the Cin front end as shown in Fig. 4, the
constants should be set in consideration of these characteristics. Using the smallest resistor Rg1 value possible is
recommended.
In addition, when setting the signal level, the voltage gain should be set on the LA4815M side and the input front-end
should be configured using only the input coupling capacitor, Cin, as shown in Fig. 5 in order to maximize the ripple
rejection ratio.
• Pins 1 and 8 be left open : Approximately 26dB
• Pins 1 and 8 connected to GND : Approximately 39.5dB
• Voltage gain setting : According to the resistor connected between Pin 8 and Pin 2 (GND1)
• Output DC voltage setting : According to the resistor connected between Pin 1 and Pin 2 (GND1)
• Voltage gain setting : According to the resistor connected between Pin 8 and Pin 5 (OUT)
• Output DC voltage setting : According to the resistor connected between Pin 1 and Pin 6 (V CC )
other IC
other IC
* Voltage gain = 20log (20 × (625 + Rvg1)/(125 + Rvg1))
* Rvg1 = Rvg2 must be satisfied.
* Voltage gain = 20log (20 × (125 + Rvg3)/(10,125 + Rvg3))
* Set the resistor values so that the Pin 5 (OUT) DC voltage is approximately half the supply voltage.
ro
ro
OUT
OUT
Rvg1
Example : When Rvg3 = 10kΩ, Rvg4 = 22kΩ (when V CC = 6V)
GAIN2
GAIN1 GND1
8
1
Rvg2
Figure 1
Figure 5
LA4815M
7
2
Cin
Figure 4
Rg2
V CC
6
3
3
Rg1
IN
Cin
OUT
5
4
LA4815M
3
LA4815M
IN
LA4815M
Rvg4
GAIN2
GAIN1 GND1
rg
8
1
Rvg3
Cin
Figure 2
LA4815M
7
2
Figure 3
IN
3
V CC
6
3
Pre-Amp
100kΩ
OUT
+
-
5
4
Vbias
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