STMicroelectronics Pop-free 120 mW stereo headphone amplifier DEMOTS488S DEMOTS488S データシート
製品コード
DEMOTS488S
Application information
TS488-TS489
22/32
Doc ID 11971 Rev 5
4 Application
information
4.1
Power dissipation and efficiency
Hypotheses:
■
Voltage and current in the load are sinusoidal (V
out
and I
out
).
■
Supply voltage is a pure DC source (V
CC
).
Regarding the load we have:
and
and
The average current delivered by the power supply voltage is:
Figure 78.
Current delivered by power supply voltage in single-ended configuration
The power delivered by power supply voltage is:
So, the power dissipation by each power amplifier is
and the maximum value is obtained when:
V
OUT
V
PEAK
ωt V
( )
sin
=
I
OUT
V
OUT
R
L
-------------- A
( )
=
P
OUT
V
PEAK
2
2R
L
----------------- A
( )
=
I
CC
AVG
1
2
π
------
V
PEAK
R
L
-----------------
t
( )
sin
t
d
0
π
∫
V
PEAK
πR
L
----------------- A
( )
=
=
Icc (t)
Time
T/2
T
Icc
AVG
Vpeak/R
L
0
3T/2
2T
P
supply
V
CC
I
CC
AVG
W
( )
=
P
diss
P
supply
P
OUT
W
( )
–
=
P
diss
2V
CC
π R
L
------------------- P
OUT
P
OUT
W
( )
–
=
P
OUT
∂
∂P
diss
0
=