Hi-fT POWER TRANSISTORS
For detailes characteristics
, refer to "
SEMICONDUC-
TOR DATA" at the end of this
manual.
The power
transistors
employed in
ALPHA 220
realize an IT
(Current Gain-
bandwidth Product) of
80 MHz with NPN type and 60
MHz with PNP type
(each being a
typical value) in
spite of its high
Pc (Collector Power
Dissipation) such as 150 W (The
value when Tc = 25
0 C). Compared with conventional
transistors with a Pc of 150
W where IT was around
10 MHz at maximum, the high speed attained by these
Hi-
IT power transistors is remarkable.
Such high IT has been
realized specially by the inside
construction of these
transistors which is greatly dif-
ferent from that of conventional ones
the multi-
emitter construction.
In this construction
, the emitter inside the
transistor
is divided into many units and emitter
resistors with
small resistance are inserted to each unit
, resulting in
a parallel connection,
Figure 3-
4 OPERATION OF BARIAVLE BIAS
I ALPHA 220
ALPHA 220
PARTS LOCATION
This equivalently means that many small signal transis-
tors with high IT and
switching speed are parallelly
connected
, which has made it possible to realize such
a high power characteristic while maintaining high
switching speed.
Thanks to
such construction as mentioned above
these power
transistors are excellent in linearity of
its hfe.
Furthermore, as dissipation is dispersed equally to
each emitter due to the emitter-
divided construction
they have another
feature of being strong
against
breakdown as compared with
conventional power
transistors.
OPI
qQD
Photo 5
C3ID
-oOUTPUT
RE2
1+--1
..,
O2 -
CID
OP2
Figure 4 VARIABLE-
BIAS CIRCUIT
Photo 6
INPUT
ei
---,
Figure 5 DC-
SERVO CIRCUIT
Photo 7
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