TS4984FC Datasheet, PDF (19/30 Pages) STMicroelectronics – 1.2W Stereo Audio Power Amplifier with Active Low Standby Mode

TS4984FC
Application Information
The output power is:
P_out
=
(_---2_----V_{----o---u---t-R----M----S----})_--²_-
R_L
For the same power supply voltage, the output power in a BTL configuration is four times higher
than the output power in a single-ended configuration.
4.2
Gain in typical application schematic
The typical application schematic (Figure 62) is shown on page 18.
In the flat region (no C_in effect), the output voltage of the first stage is:
V_out1
=
(
–V_i
n
)
R_{-----f--e---e---d-}
R_in
(V)
For the second stage:
V_out2 = -V_out1 (V)
The differential output voltage is:
V_out2 – V_out1
=
2
V_i
n
R_{-----f-e---e---d--}
R_in
(V)
The differential gain, referred to as G_v for greater convenience, is:
G_v
=
V_{-----o---u---t-2----–-----}V_{----o---u---t--1-}
V_in
=
2R----_R-^f--^e-_i-_n-^e---^d-
V_out2 is in phase with V_in and V_out1 is phased 180° with V_in. This means that the positive
terminal of the loudspeaker should be connected to V_out2 and the negative to V_out1.
4.3
Low and high frequency response
In the low frequency region, C_in starts to have an effect. C_in forms with R_in a high-pass filter with
a -3dB cut-off frequency:
F_CL
=
-----------¹-------------
2πR_inC_in
(Hz)
In the high frequency region, you can limit the bandwidth by adding a capacitor (C_feed) in
parallel with R_feed. It forms a low-pass filter with a -3dB cut-off frequency. F_CH is in Hz.
F_CH
=
-----------------¹-------------------
2πR_feedC_feed
(Hz)
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