TDA7294_07 Datasheet, PDF (11/17 Pages) STMicroelectronics – 100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY

Figure 19: P.C.B. and Components Layout of the Circuit of figure 18 (1:1 scale)
TDA7294
diodes Z1,Z2 and resistors R7,R8 define the mini-
mum drop across the power MOS transistors of
the TDA7294. L1, L2, L3 and the snubbers C9,
R1 and C10, R2 stabilize the loops formed by the
"bootstrap" circuits and the output stage of the
TDA7294.
In figures 21,22 the performances of the system
in terms of distortion and output power at various
frequencies (measured on PCB shown in fig. 19)
are displayed.
The output power that the TDA7294 in high-
efficiency application is able to supply at
Vs = +40V/+20V/-20V/-40V; f =1 KHz is:
- Pout = 150 W @ T.H.D.=10 % with Rl= 4 Ohm
- Pout = 120 W @ " = 1 % " " "
- Pout = 100 W @ " =10 % with Rl= 8 Ohm
- Pout = 80 W @ " = 1 % " " "
Results from efficiency measurements (4 and 8
Ohm loads, Vs = ±40V) are shown by figures 23
and 24. We have 3 curves: total power dissipa-
tion, power dissipation of the TDA7294 and
power dissipation of the darlingtons.
By considering again a maximum average
output power (music signal) of 20W, in case
of the high efficiency application, the thermal
resistance value needed from the heatsink is
2.2^oC/W (Vs =±40 V and Rl= 4 Ohm).
All components (TDA7294 and power transistors
T1 and T2) can be placed on a 1.5^oC/W heatsink,
with the power darlingtons electrically insulated
from the heatsink.
Since the total power dissipation is less than that
of a usual class AB amplifier, additional cost sav-
ings can be obtained while optimizing the power
supply, even with a high headroom.
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