TS4984FC Datasheet, PDF (24/30 Pages) STMicroelectronics – 1.2W Stereo Audio Power Amplifier with Active Low Standby Mode

Application Information
TS4984FC
4.9 Application example: differential-input BTL power stereo
amplifier
The schematic in Figure 67 shows how to design the TS4984 to work in differential-input mode.
For this discussion, only the left-channel amplifier will be referred to.
Let:
R_1R = R_2L = R₁, R_2R = R_2L = R₂
C_inR = C_inL = C_in
The gain of the amplifier is:
G_Vdif=
2
R_-----2_--
R1
In order to reach the optimal performance of the differential function, R₁ and R₂ should be
matched at 1% maximum.
Figure 67. Differential input amplifier configuration
Neg. Input LEFT CinL
R1L
Pos. Input LEFT CinL
R1L
R2L
StandBy
Control
R2L
VCC
IN-L _-
IN+L ₊
Cs
TS4984
VO-L
StandBy _Bias
BypassL
-
AV = -1
+
VO+L
LEFT Speaker
8 Ohms
Pos. Input RIGHT CinR
R2R
R1R
Neg. Input RIGHT CinR
R1R
IN+R ₊
IN-R _-
BypassR
Cb
VO-R
-
AV = -1
+
VO+R
RIGHT Speaker
8 Ohms
R2R
The value of the input capacitor C_in can be calculated with the following formula, using the -3dB
lower frequency required (where F_L is the lower frequency required):
C_in
≈
---------¹-----------
2πR₁F_L
(F)
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