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Page Title:
Figure 4-3. Main control circuit, simplified schematic diagram. |
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  held constant, by reference diode CR4, more
er potential and therefore the base of Q13
is also at a higher potential. This causes more
current flows in Q15 and its collector resistor
R20. The collector of Q15 and the base of
current to flow in Q13 and tends to raise the
voltage at Q12 and Q13 emitters. Since the
Q13 tend to go down, causing less current to
flow in Q13. The emitters of Q12 and Q13 are
current in Q14 tends to rise, the current in
now at a lower potential, and because the base
collector resistor R18 also tends to rise. This
of Q12 went up, more current flows in this
action brings the collector of Q14 and the base
transistor. This action causes more current to
of Q12 to a lower potential. Since the base
flow in the base circuits of Q10 and Q11.
potential went down and the emitter potential
More current now flows in Q10, and more pos-
went up, Q12 tends to cut off, and there is
itive bias is applied to the base of the passing
less current available to the bases of Q10 and
transistors, in the master passing stage (Q2,
Q11. Less current flows in Q10 and therefore
less positive bias is applied to the base of the
Q4, Q6, fig. 4-2). The impedance of this stage
is thus lowered, restoring the output voltage.
passing transistors in the master passing stage
The differential amplifier develops a regulated
(Q2, Q4, Q6) (fig. 4-2). The impedance of
these transistors goes up and thus restores the
voltage across R22-R25. This voltage main-
tains constant current through the sensing cir-
output voltage. If the output falls, because
of line or load change, the base of Q14 tends
cuit, with R30 and R31. The value of R30 and
to fall and less current flows in this transistor
R31 adjusts the output voltage. Capacitor C17
and its collector resistor R18. The potential at
presents a low impedance to the ripple current,
the collector of Q14 and the base of Q12 tends
and a low impedance path for the ac signal to
to rise. The emitters of Q14 and Q15 go to a
the main amplifier.
lower potential and since the base of Q15 is
Main control circuit, simplified schematic diagram.
4-4
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