LA4182 Datasheet, PDF (4/9 Pages) Sanyo Semicon Device – 2.3 W 2-Channel AF Power Amplifier

LA4182
Description of External Parts
C1(C2) Feedback capacitor
C3(C4)
C5(C6)
Bootstrap capacitor
Oscillation preventing capacitor
C7(C8) Output capacitor
C9
Decoupling capacitor
C10
Power source capacitor
The low cutoff frequency depends on this capacitor. If the capacity is increased,
the starting time is delayed.
If the capacity is decreased, the output at low frequencies goes lower.
Polyester film capacitor, being good in temperature characteristic, frequency
characteristic, is used. If an aluminum electrolytic capacitor or ceramic capacitor
is used, oscillation may occur at low temperatures.
The low cutoff frequency depends on this capacitor. In order for the low
frequency characteristic in the bridge amplifier to be equal to that in the stereo
amplifier application, the capacity must be doubled.
Used for the ripple filter. Since the rejection effect is saturated at a certain
capacity, it is meaningless to increase the capacity more than needed. This
capacitor, being also used for the time constant of the muting circuit, affects the
starting time.
Application Circuit
1. Voltage gain adjustment
k Stereo
The voltage gain depends on built-in resistors R1 (R2),
R3 (R4) as follows :
VG = 20log ^{R3 (R4)} [dB]
R1 (R2)
If the IC is used at a voltage gain less than this, the
following equation with Rf added applies.
R3 (R4)
VG = 20log _{R1 (R2) + Rf [dB]}
where R1 (R2) = 50 Ω, R3 (R4) = 10 kΩ
k Bridge
The above shows the bridge amplifier configuration, where ch.1 operates as a noninverting amplifier and ch.2 as an inverting
amplifier. The output of ch.1 is divided with R5, R6 and led to pin 1 and then input to ch.2.
Since the attenuation degree (R5/R6) of ch. 1 output and the amplification degree (R4/R2 + R6) of ch. 2 are fixed at an equal
value, the ch.2 output is in opposite phase with the ch. 1 output. Therefore, the total voltage gain gets apparently 6 dB higher
than the voltage gain of ch.1 alone and is determined by the following equation.
VG = 20log ^R3 + 6 [dB]
R1
If the IC is used at a voltage gain less than this, the following equation with Rf added applies.
VG = 20log ^R3 + 6 [dB]
R1 + Rf
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