ITT - Index of

TBASOO
5 WATT AU 010 AM PLiFIER
CIRCUIT LAYOUT
RECOMMENDATIONS
The side heat tabs help to ensure that the
maximum junction temperature of 150°C is not
exceeded. These tabs alone, suffice for output
power not exceeding 2.5 watts. However,
for high output power extra heat sinking must
be provided. For example, the tabs can be
soldered to a printed board copper area for
heat sinking (Fig. 16) purposes. With a thickness
of 35p.M the required square side dimension
L may be obtained from Fig. 9. This
applies for an Tamb=55°C.
CALCULATION OF REQUIRED COPPER PC
BOARD AREA
1) Calculate max. power dissipation
,(Vee max)2 V
P'o' = 0.4' ~ + ee max' IQuiescent
Where Voemax=Vce+10% if not stabilized
RL = load resistance. IQulescen' can be obtained
from Fig. 8. For worst case analysis use
IQule,cent at 20 rnA for 24V supply voltage.
2) From Fig. 9, one can obtain the minimum
side length of the square heat sink.
Example
a) Vce=24V. unregulated, RL =160
P tot=O.4 (24+2.4)2+
8.16
(24+2.4) X20X 10 .'=2.6W
From Fig. 9 obtain L=app. 25 mm.
For geometries different from the one of Fig. 16 note that copper areas
(lear the tabs have better efficiency as regards power dissipation. There.
fore additional safety factors must be added for worst case designs.
b) Vee=12V regulated, RL =8{}
Ptot =0.4x 12·+12X20X10 '=1W
8.8
From Fig. 9 it is seen that for TA~55°C, no
extra heat sinks are necessary.
W
10
TBA 800
THO=10·'.
(=1 kHz
8
, / /
RL=8Q V IL
1?L=16Q
/
/ V
2
/ V/
o o
~
5 10 15 20 25V
_vcc
%
10
18
,
,
2
VCC=2' V
RL =16Q
f = 1 kHz
2
J
I
1
TBA 800
J
,
6 8 lOW
-Iil
Fig. 3-0utput power versus supply voltage
(circuit as Fig. 2)
Fig. 4-Totai harmonic distortion versus output
power (circuit as Fig. 2)
8-71