and the voltage between R16 and
inates noise introduced by the powerline. The
R17 becomes more negative. More
main power supply furnishes approximately
current flows through R16 to the
+ 43 volts dc.
base of Q2. The base-to-emitter cur-
d. Auxiliary Power Supply. The ac voltage
rent flow of Q2 increases. This
causes a much greater increase in
tified by diodes CR3 and CR4 and filtered by
the collector-to-emitter current
capacitors C3, C4, and C5 and resistors R2, and
More current
flow through Q2.
R3. This rectified voltage is applied to ampli-
flows through resistor R6 to the
fier transistors Q2 and Q3, and emitter follow-
collector of Q2, and the voltage
er transistor Q4, and is also used to bias the
drop across R6 increases. The volt-
base of regulator transistor Q1. The auxiliary
age between R5 and R6 becomes
power supply furnishes approximately -20.4
less negative, and less current
volts dc.
flows through R5 to the base of
e. Regulator. The regulator circuit provides
regulator Q1. The base-to-emitter
voltage and current regulation to maintain the
current flow through Q1 decreases.
power supply output voltage and current at a
constant level as set by the front panel con-
of Q1 increases, and more voltage
trols.
is dropped across Q1. The in-
(1) Voltage regulator. The voltage regu-
creased voltage drop across Q1
lator circuit consists of transistor Q1,
compensates for the initial rise in
capacitor C7, diode CR6, and resistors
the power supply output voltage,
R4, R5, R7, R8, and R16 through
thereby maintaining the output
R21. The collector of Q1 is connected
voltage at a constant level.
to the negative side of the main pow-
(b) When a change occurs causing the
er supply dc output. The base of Q1
power supply output voltage to
is biased by resistor R4, and the
decrease, less current flows through
emitter is biased by resistors R7 and
resistor R19, and more current
R8 (short-circuit current adjust).
flows through resistor R18 to the
The output voltage is set by VOLT-
base of Q3. The base-to-emitter cur-
AGE ADJUST resistor R19 from
rent and the collector-to-emitter
the front panel. Capacitor C7 bypass-
es R19 to provide a constant maxi-
current flows through R17 to the
collector of Q3, and the voltage be-
from the power supply dc output. Re-
tween R16 and R17 goes in a posi-
sistor R20 presents a constant cur-
tive direction. Less current flows
rent source to the junction of resis-
through R16 to the base of Q2. The
tors R18 and R19 and, hence, to the
base-to-emitter current and the col-
base of Q3.
lector-to-emitter current through
Q2 decrease, and less current flows
(a) When a change occurs causing the
through resistor R6 to the collector
power supply output voltage to rise,
of Q2. Less voltage is dropped across
part of the electron flow through
R6, and the voltage between R5
resistor R18 to the base of Q3 is
and R6 becomes more negative.
diverted through resistor R19. This
More current flows through R5 to
reduces the base-to-emitter cur-
the base of regulator Q1. The
rent flow of Q3 which, in turn,
base-to-emitter current flow of Q1
reduces the collector to-emitter cur-
increases, and the collector-to-emit-
rent flow.
Reduced collector-to-
emitter current flow through Q3
age is dropped across Q1, and the
decreases the current through R17.
Less voltage is dropped across R17,
4