Advertisement
CIRCUIT DESCRIPTION
DARLINGTON CONNECTION
A class-A circuit
in the preamp
employs
Darlington
connection.
The load of input stage used current mirror
circuit,
which
is a kind of constant current circuit, and
the constant
current
circuit
has high impedance
in AC
circuit.
The Darlington connection is obtained an increase
of hfe and
input impedance.
Zin= hfegX hfeli* RL
le9= lb9 X hfes
lott=Ibtr™ hfett= (bet tes)
X hfell
IT =I09+ Ioli= Ibo hfeg+ (lb9-+ Ibs hfes)hfet!
entire hfe
hfe== 17 /1b9
hfe== (hfegt+ t)Chferi4+ t)
|
hfeat+ | hfe
nfe= hfe
hfe
TONE AMP
The flat amp in tone circuit employs
ICL circuit with
FET
like the preamp.
The
load of the second
stage is
constant-current
circuit.
Gain
control
is obtained
from varing the amount
of
feedback.
Bass and treble tone amplifier are independence,
but it 1s O-dB.
{CL
input.
Flat
stage with
amplifier
FET
~ Constant-
current
=
$:
=e
Ri22
18K
Turnover
trequency
(TREBLE)
%0
%
ORE
Turnover
On
frequency
}
aa
(BASS)
f
oti en nnne Seannnnenren
os
Rie
L.
ae
i
ae
J
ot
ee
150Hz
400Hz
3kHz
6kHz
Frequency
POWER AMPLIFIER
uPA 63H
< Equivalent Circuit of uPA 63H >
Advertisement
