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1
5.2 CIRCUIT DESCRIPTION
QQ
3 7 63 1515 0
A
VOLTAGE AMP UNIT
B
R103
1k 1/4W
AMRS
C125
C129
R101
C
TE
L 13942296513
R104
1k 1/4W
AMRS
D
E
This circuit is a voltage amplifier stage of 30-dB gain.
The input block (Q101, Q102, Q103, and Q104) is a buffer
amplifier. A current mirror circuit has been adopted as a constant
current circuit. Operating it on constant current reduces any
influence of temperature drift. A diamond buffer circuit is
constructed by cross-connecting this circuit and the initial stage of
the amplifier section.
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The signal voltage attribute that is input to the initial stage (Q107,
Q108, Q109, and Q110) of the amplifier section is converted to
current via the current mirror circuit (Q113 <=> Q115, Q114 <=>
Q116). A Wilson Mirror circuit has been adopted as a current mirror
circuit, for higher accuracy.
F
The V/I converted current attribute is converted to voltage with the
aid of the input impedance of the SEPP circuit at the output buffer
(Q121, Q122) then output.
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2
DC ADJ
R117
100 1/4W
R113
47 1/4W
C127
AMRS
2200p/125V
R114
AMCH
47 1/4W
AMRS
R118
100 1/4W
R147
47 1W
CM1
x
ao
y
.
i
2
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8
Q115
2SA970(BL)
Q119
2SA1145(OY)
R125
100 1/4W
IDOLE ADJ
R127
33k 1/4W
R128
33k 1/4W
Q Q
3
6 7
1 3
Q120
2SC2705(OY)
R126
100 1/4W
Q116
2SC2240(BL)
R146
R145
750 1W
750 1W
CM1
CM1
To improve the high-frequency characteristics, a cascode bootstrap
configuration (Q111, D101, Q112, and D102) at the initial stage
improves the high-frequency characteristics.
The negative feedback (NFB) is applied from the output stage to
the β circuit that consists of R145, R146, and R147. When the
feedback is applied to the emitter that is located at the initial stage
of the amplifier section, where the impedance is low, the NFB
current flows and serves as the current feedback.
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As described above, a high-accuracy circuit is adopted in each
part, and a simple configuration is adopted in which the voltage
attribute is converted to current then reconverted to voltage in one
.
stage. Combined with a current feedback configuration, all these
features achieve a highly stable amplifier.
TAD-M600
3
4
2 9
9 4
2 8
TO POWER AMP ASSY
CN104
B4B-EH
V+55
C115
!
100p 125V
R133
220 1/2W
AMCH
Q121
2SC4883A(Y)
!
!
1 5
0 5
8
2 9
9 4
Q122
!
2SA1859A(Y)
R134
220 1/2W
C116
100p 125v
AMCH
m
co
4
9 9
+55V
!
2 8
9 9
!
-55V
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