Luxman l 100 service manual

Page 2

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CIRCUIT DESCRIPTION

1)

S

P Q207

0211
Q209

J 0.3hmA LPmA

OUT
>- fl 0
1/2.5
\J 0. 3AmA b
SmA
leA
0210
Q212

£§s;}:} LINEAR EQUALIZER

Equalizer Stage

At the lst stage 0203 and Q2010 operate as a differential amplifier. 0201 and 0202 prevent
the high frequency characteristics from deterioration, which may be caused by the change of the
feedback amount originated by the fluctuation of the base-collector voltage of Q203 and QZOA in
accordance with the input signals. Constant current is applied to these common emitters of
Q203 and (2204 to obtain better DC stability and to increase CMRR (Common Mode Rejection Ratio).

The next stage is composed by (2207 and Q208 together with the constant current load. (2208
operates same as Q201 and 0202 at the let stage. The tZOV constant voltage driving is applied
by use of a zener diode up until this stage. The Inverted Darlington configuration by Q209,
Q211 and QZlO, 0212 is adopted in the output stage. At the same time some 8dB gain is obtained.

A high voltage of :431 is applied to ensure sufficient output voltage; maximum 27Vr.m.s.
The transistors Q201 and (1208 are arranged to assist Q203 and Q202 respectively in order to
operate them in the optimum condition. It is able to consider Q209 and Qle, or Q210 and Q212

to be one equivalent transistor, therefore the equivalent circuit should be as the fig.l-2.

IN

-iCLlC.

L INEAR EQUAL IZER

OUT

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