Werbung
we
wn
en
ee
tae
ce
cee eee
:
tet e
e i
Se
rae
Se
= SERVICE AID
At the initial stage of the main amplifier of this unit, the differential
amplifier of current mirror load is employed.
This is a circuit for obtaining the gain higher than that in the conventional
circuits, with current in the differential amplifier stage kept constant.
|
When
!cl
is increased
through
variation
of base voltage of the differential
amplifier TR1,
lc2 at TR2
is reduced with consequent decrease in the voltage
drop at R2, this in turn reduces VEB
of TR3, and thus |!c1 gradually decrease.
On the contrary, when
!Ic1 of TR1
is reduced, Ic2 of TR2 is increased with
increase of voltage drop at R2, thus resulting in rise of VEB for TR3 and conse-
quent increase of Icl.
As the characteristics of the differential amplifier, 1c2 is
reduced..as
Icl is increased.
!n this way,
!c1 and !c2 are kept constant at all
times through functioning of TR3.
Constant
current
means that high impedance
is connected to the differential
amplifier circuit, and thus large voltage gain can be obtained. Another cause for
increasing the voltage gain is the push-pull circuit formed by TR71 and TR3.
In
the differential amplifier, signal of Opposite phase is obtained at the collector of
TR1
with respect to the input signal, while in the collector of TR2, signal of the
phase as the input is obtained to be further applied to the base of T-R3.
Accordingly, signal of opposite phase to the input is developed at the collector
of TR3, thus consequently forming the push-pull circuit of TR1
and TR3.
Jn
other words, since the amount of NF can be increased with the rise of the gain, -
improvements in the distortion factor and S/N ratio can be achieved.
OUTPUT
(CURRENT MIRROR CIRCUIT)
Fig. 1
1. Dial cord length is 200 cm ( 7834').
Oy.
2. Tuning gang Is positioned at maximum
a——_—
capacity. (Frequency is minimum)
3. Arrow
marks
(1 ~ 9) indicated
correct order and
direction of
3
Stringing dial cord.
SA-5370
Printed in Japan
7706-8500 ©
¢
in
eet
a
Werbung
